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R2E Review – November 2011 November 21st – 24th

R2E related preparations for both, this xMasBreak and LS1 are already in full preparation.

This together with the analysis based on 2011 operation led to the proposal of a dedicated

R2E review (see schedule) with the program and presentations also available at:

http://indico.cern.ch/event/R2E_Review_2011

Sandwiched between an introduction and a planning/resources/strategy session, four

technical sessions were held:

- Introduction

- Calculations and monitoring: radiation levels, operation, future development

- Radiation tests & failures: observed failures, facilities and results, preparations and

requirements

- Power-Converters & Super-Conducting Links: radiation tolerant power-converter

R&D program, development of super-conducting links and best long-term strategy

- Implementation & Integration: xMasBreak 2011/12 and LS1 mitigation actions

- Summary, Resources & Strategy: planning, available and required resources.

For each session a set of questions/discussion points has been made available to the

speakers during the preparation of the talks (see original planning document). Based on

this a “review guideline document” was distributed to the reviewer to ease the analysis of

each of the sessions.

In the following we briefly summarize each session objective, highlight the main conclusions

with the emphasis on follow-up actions to be taken.

A brief summary of the R2E activities over the last year together with an overview of the

program, the session chairs, secretaries and reviewers is available in the Appendix.

The review sessions were arranged in order to optimize people‟s presence and required

expertise by grouping together the respective current R2E main concerns. For the first three

technical sessions (calculations & monitoring, radiation testing & failures and the power-

converter R&D program), together with the internal reviewers, external reviewers kindly

agreed to participate and help.

A lot of R2E related work has been performed during 2011 as nicely shown

throughout the numerous and very detailed presentations The R2E project and

review organizers would like to thank all the reviewers, speakers and helpers for

making this review/workshop a success and bringing the R2E project an important

step forward.

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Session - 0: Introduction: Aim of the review + Performed Actions

This introduction session aimed in setting the scene for the review by giving a brief

overview on what failures were observed and what mitigation measures were implemented,

together the operational experience from the experiments as well as what the LHC

management expects from this review and the R2E project in general.

Identified follow-up actions:

- Continued staged approach of mitigation actions.

- High-priority for failure analysis and tests also for 2012.

- Mitigation measures must allow up to 20fb-1 for 2012 and 2x1034 (>40fb-1) after LS1.

- R2E measures and new developments should not neglect the requirements for

beyond nominal LHC (ultimate & upgrades)

The main conclusions are summarized as:

- Expectations for LHC Performance (2012)

o The SEEs should allow for an increase in peak luminosity by around a factor

of two or more, and an integrated luminosity of ~20 fb-1.

- Expectations for LHC Performance (After LS1)

o The SEEs should allow for a peak of 2x1034 with an integrated luminosity of

>40fb-1

- We have a long, complicated, and costly project ahead of us in the coming years

o We need a staged approach so that we can mitigate against SEEs as the

machine performance increases (shielding, redesign, relocation)

o A very logical and pragmatic approach has been followed so far and should

be preserved, continuing with a staged implementation of mitigation measures

is important to keep the balance and optimize the mitigation measures

o This review should define the priorities for the next steps (years)

- Experiments and SEE failures:

o SEU‟s have been taken into account during the design phase of the

electronics in the experiments from the “early” days of the designs

o Different parts of systems have very different criticality and it‟s important to

note that intrinsic redundancy in tracking detectors leads to the fact that no

operational constraint is given if the system is operational at a level higher

than 95% (this is different for LHC critical systems where single failures of

critical systems lead to a beam-dump)

o With the current LHC luminosity SEUs do not pose problems for the running

of the LHC experiments and observed SEU rates seems to match initial

estimates quite well

o For future upgrades radiation effects are again being seriously considered,

further emphasized by the increased sensitivity of modern technologies and

the fact that chips are likely to be also more complicated

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o Safety factors of x5 for radiation levels were applied as design constraints;

today‟s operation and monitoring shows consistencies within a factor of two.

- Clear criteria were applied for the analysis of radiation induced problems in the LHC;

this required and will continue to require a significant amount of work (high priority for

2012)

- Number of failures (proton run only):

o Total (dump, no-dump, confirmed, not-confirmed): 237

o Beam-Dump:

Confirmed: 63

To be confirmed: 18

o No-Dump: 156

Confirmed: 142

To be confirmed: 14

- A lot of work has been done by the equipment groups -> patch solutions in order to

avoid problems showed to be not only efficient, but a clear requirement to allow for

acceptable LHC performance

- Radiation levels were measured in detail around the LHC and in all critical areas.

Measurements nicely confirm the original estimates based on FLUKA calculations

considering the real operational parameters of the LHC.

- Defined priorities for staged mitigation measures (shielding, relocation and new

design) have proven to be efficient and allowed for optimization throughout the years

- Mitigation measures performed during the last year allowed to limit radiation induced

failures so that the 2011 operational reach remained achievable

- For the LHCb upgrade an annual luminosity of 10 fb-1 should be taken into account

for requirements beyond nominal LHC operation

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Session – 1: Calculations & Monitoring

This first technical session aimed in having a critical look on our understanding of radiation

levels in the LHC and their evolution with time (today and future). This includes a few

unknowns, e.g.: the evolution of the residual gas pressure close to various critical LHC

areas and how much the loss distribution would change for the LHC collimation system.

Our „eyes‟ of the LHC being the installed monitoring and for electronics in particular the

RadMon system, we‟re strongly depending on how well we actually understand their

calibration and related uncertainties. Their measurements can then be compared to

performed Monte-Carlo calculations, allowing to further refine our critical area overview, but

also highlighting a few important points to be clarified concerning the monitoring unit:

RadMon sensor calibration and accuracy of measurements and what uncertainties have to

be taken into account for the reported radiation levels; what future sensors could be used in

order to improve the current design limitations. This leads to a required analysis whether

the coverage of monitors is sufficient in order to follow and evaluate both, the LHC radiation

levels, as well as the effectiveness of planned/applied mitigation measures. In addition, with

present radiation test facilities having a strong limitation in several aspects, a first study was

performed towards a future radiation facility which would allow equipment groups and

projects performing their radiation tests in a much more efficient and complete way.

Identified follow-up actions:

- Dedicated neutron spectra measurements in LHC critical areas are to be performed

to conclude on comparison between measurements and simulations.

- Dedicated thermal neutron sensor (e.g. back-to-back pin-diodes with Li6) for the 2nd

generation RadMon development to be studied. A „semi-commercial‟ readout version

seems also to exist.

- The RadMon development for the 2nd generation with a new set of sensors in order

to also increase the dynamic range is to be continued with high priority (aiming for

first installations during LS1).

- Further available calibration data of the Cypress memory needs to be investigated.

- Additional (alternative) monitor locations are to be reviewed for this xMasBreak, both

for active (RadMons) and passive monitors (e.g. TLDs).

- The ion operation and respective losses in the dispersion suppressor are to be

studied further.

- The 25ns scrubbing period foreseen for early 2012 shall also be used in order to

conclude on the future average residual gas densities in the DS and ARC –

dedicated beam-time likely to be necessary.

- Further analysis and (BLM) studies are required to understand the sharing of

collimation losses between IR3 and IR7, as well as the impact of tight collimator

settings on the loss distribution within the insertion.

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The main conclusions are summarized as:

- Thermal neutrons in the LHC tunnel and shielded areas:

o The reviewers reiterate that the measurement of the thermal neutron fluence

provided by the RadMon devices is not judged to be very reliable. The new

electronics which will be installed in the future should be less and less

sensitive to thermal neutrons; nevertheless we should/could measure the

neutron fluence in current LHC critical areas by means of some independent

and calibrated devices, such as the MediPix with suitable converters.

o New generation RadMons should also allow the measurement of the thermal

neutron fluence, e.g., with back-to-back pin-diodes loaded with Li6 (to install

during LS1 to monitor >2014 operation).

o The spread of components (batch, etc.) is expected to be higher for already

'normally‟ sensitive components which are operated at the edge of their

specifications. While new technologies are rather immune against thermal

neutrons (due to the removal of the boron-glass from the production process),

it‟s important to note that for recent technologies <45nm thermal neutrons

again start playing a role), the latter confirming that the independent

measurement of the high energy and thermal neutron component is to be

clearly separated.

- Comments on the RadMon monitoring:

o The range of measurement should be extended and in particular new

memories should be actively investigated in such a way that the sensitivity

might be extended to less than 106 HEH/cm2. This is particularly true as

RadMons might be placed in locations where electronics will be relocated and

lower radiation levels are to be expected. To increase sensitivity a higher

cross section is needed and this can be done by increasing the cross section

per bit or the number of bits. It‟s important to note that more recent memories

have a generally a lower cross section per bit, but MEU sensitivity increases.

Technology below 65nm may also be sensitive to direct ionization effects

o A possible memory candidate is the studied Cypress one. Besides the

measurement carried out at CERN, also other calibration data is available by

the reviewers. MBU could be a possible point to be considered (no bit

scrambling), however expected (from a preliminary analysis) to be less than

10%. The Cypress SRAM having a feature size of 90nm, it will be important to

analyze the proton cross-section at various energies, the ideal case being

having a very low proton energy threshold in order to detect all HEH. The fact

that there is no bit-scrambling indicate that the device may indeed be

sensitive to MBU (see comment above). An additional important issue to be

considered are MEUs (several upsets in neighbouring memory cells created

by one particle) and also this should be well characterized.

o The reviewers suggested that a modular design should be actively

investigated in order to tackle eventual new effects on the long term (and

therefore new types of chips).

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o Only two RadFETs with one at 100nm and one at 1650nm could be used.

o For the BatMons it‟s suggested to optionally use locally available power

instead of batteries, allowing more independent functioning with less risks of

battery overtime (and eventually Wireless, even though this readout system

would have to be sufficiently radiation tolerant).

o A stock of spare RadMon and BatMon should be kept in case of urgent needs

(as already encountered during 2011 operation).

o Monitoring should be added to the UX25 cavern at the weakest point for

electronics. In the meantime, one could use the PMI to get an idea of the

levels to be expected.

o Calibration:

RadFets: while observations (at CNRAD) could propose possible low-

DR effects, additional measurements performed at H4IRRAD don‟t

seem to support this assumption. The proposed biasing of Vg is not

considered as a good option to improve the current conditions. Further

investigations are required, with particular emphasis on fading. It was

agreed that available measurement results are to be distributed for

further analysis. A more accurate fading study is recommended.

PIN-diodes: it‟s important to note that the existing calibration can cause

a significant error at low-fluences, however this being a systematic

error an automatic correction through look-up tables is possible and

required.

SRAMs: the finally assumed spread of chips is about 40%, while the

boxes (4-8 chips) will likely profit from the mixture between various

chips (averaging effect), thus having a lower average error. For the

future RadMon memories with less variability between parts are to be

chosen.

- Investigation of the ion run radiation field:

o Based on 2011 ion operation, it seems that in the long term the radiation

levels in the DS of P1/2/5 (not P3/7) will be dominated by the ion losses. This

situation might change once P1/5 collimators are fully installed and at working

at nominal settings.

o An investigation to understand which ion species are contributing most at

what critical location would be needed as well as what might be the impact of

the possible DS collimators; these last points are not necessarily required by

the R2E activities.

- Issue on beam gas for >LS1 operation (25 ns):

o As the pressure levels during 25ns batch spacing operation are still partially

not clarified (which might lead to different requirements of TID for equipment

in the ARC), the reviewers suggests to perform a long 25ns scrubbing run

during 2012 –including 3.5/4 TeV ramps – to observe the evolution of the

pressure levels on a longer scale.

o In order to measure realistic beam-gas radiation levels stable beam periods

are required.

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o The effect depending on the threshold and then also limiting LHC

performance it is likely that the levels in the ARC are limited to 10-8, thus

suggesting that long-term annual average values lie significantly below.

- Effect of collimators settings on P7 (partly) shielded areas (UJ76, RR73/77)

o The impact of “tight” collimation settings on the radiation levels in the shielded

zone of P7 has to be studied further as not all the aspects are completely

clarified yet. A more detailed analysis with the BLM team is required and will

be performed in the coming weeks.

o The loss sharing between P3 and P7 seem to be fluctuating significantly as a

function of the year and have to be further investigated. The eventual need of

passive absorbers at the momentum cleaning insertion is suggested.

o A distinct spike can be observed at the BLMs during the starting period of

stable beams, the origin being unknown so far.

- Passive dosimeters

o The reviewers suggest the use of passive dosimeters at locations where

electronics is located and to further study the impact of particle spectra on

dose measurements.

o A cross-check between these detectors and RadFETs should be pursued in

specific locations.

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Session – 2: Radiation Testing, Equipment Failures

This session focused on performed radiation tests, obtained results and how they relate to

LHC observations. A summary was provided of the radiation induced failures during 2011

LHC operation, with the observed failure modes and what equipment groups were impacted

most. Throughout the year a lot of effort was put into the detailed analysis of possibly SEE

induced failure candidates. Numerous radiation test campaigns were performed and can be

divided into two categories: (a) new developments and component testing; (b) evaluations

of existing systems. CNRAD tests focused on existing LHC equipment, the lessons learned

and what will be the impact on LHC operation. With PSI a special agreement for beamtime

during the weekend has been obtained for regular (up to one per month) irradiation slots

and tests have been used for monitor calibration, component tests and prototyping. In

addition, with H4IRRAD a new test area has been created with the focus on testing

complex (partly heavy) systems requiring special services (e.g. water cooling), allowing to

analyse in more detail the behaviour of LHC power-converters, GTOs and safe-room

equipment under radiation.

A critical review became necessary in order to question the representativeness of our test

strategy (PSI, CNRAD + H4IRRAD) with respect to final LHC conditions (shielded

areas/tunnel). A first dedicated analysis has been performed together with an external

company (TRAD). Based on this and together with theoretical and Monte-Carlo simulation

we are now confident in our chosen approach for radiation test, however still seek to further

optimize the requirements (especially for destructive tests, latches or similar) and evaluate

practical approaches in order to limit the overall test requirements.

The possibility to test components/cards/systems in an „easy‟ way is crucial for any new

development and equally important to verify envisaged patch-solutions for existing

equipment. The accessibility of representative radiation test facilities and their relevance for

the LHC radiation field is of utmost importance.

Identified follow-up actions:

- RadMon development: in order to anticipate availability issues, new memory

candidates (especially the Cypress) are to be purchased as soon as possible.

Additional sensors for TID and thermal neutrons are to be evaluated (see also

session-1).

- For destructive tests, PSI shall be used to define a first selection process of

components. Due to the maximum energy limitation at PSI (230MeV) heavy-Ion tests

are to be performed for those being considered as also system critical and where

mitigation by design is not possible. Validation on the card/system levels should be

done through a mixed-beam facility.

- TID effects are to be considered already at the design level, with verification

measurements only on critical components, on the system (prototype) level and by

foreseeing the option of rotating locations (more or less exposed) in the LHC. The

system design must account for TID effects also by including possibilities to measure

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the TID impact on the system level in order to allow anticipating failures and/or

mitigation measures (such as exchange of unit and/or locations).

- For component purchase campaigns it is recommended to evaluate the option of

buying single lots from the producer/distributer by paying higher prices.

- A new radiation test facility serving both the accelerator and the physics community

is considered as high priority in order to assure radiation tolerance requirements for

the A&T sector. Besides large irradiation volumes, easy accessibility and design, a

new radiation test facility should also foresee enough flexibility in order to allow tests

also in neutron dominant and low-dose exposures conditions. The proposed facility

in the CERN East-Area is considered as a very good possibility.

- Radiation designs shall continue soliciting external components for specific

component tests. Modularities are to be reviewed and clear procedures to be set up.

- Radiation induced equipment failures in the LHC shall be continued to be analysed

in detail. Support from the concerned equipment groups (all having equipment

exposed to radiation) is critical for the analysis process and required mitigation

measures.

- System tests on equipment failing in the LHC shall be continued, however including,

whenever possible, additional monitoring options in order to investigate at the same

time also respective patch solutions. Systems designed outside CERN need special

care and vendors shall use whenever possible limited sources of parts and assure

traceability. Test requirements have to be adjusted accordingly.

- Follow-up of LHC SEE induced failures shall continue with high-priority, respective

resources (similar to 2011) are required.

- Concerning the analysis of radiation tests the concept of „average time to failure‟

shall be adopted, with respective „failure budgets‟ being assigned for each

equipment group having equipment exposed to radiation, this way controlling the

global impact of radiation induced failures

- High priority developments concern the Power-Converter 600A AC/DC converter, the

FGClite and the QPS equipment, the latter considering a staged radiation test

approach to be followed closely.

- Design reviews are to be organized regularly between CERN internal and external

experts in order to continuously review the qualification process.

The main conclusions are summarized as:

- Target radiation limits have been defined for each critical LHC area, see also notes

on Session-1. Depending on the area, all radiation effects (SEE, TID and DD) are to

be considered, while destructive events are obviously the most penalizing. It‟s thus

important to evaluate the advantages/risk taken by doing tests at PSI and/or at

CERN mixed-beam facilities, especially for particles in the energy range of 250 to

800 MeV:

o The reviewers agree that destructive events are the major concern to take into

account for the radiation tests of the new radiation tolerant developments for

the LHC. Given the LHC radiation environment, they suggest to use the PSI

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facility at 230 MeV to make a selection of the component candidates. Heavy

Ion tests then are suggested to confirm the PSI results. If the LET threshold

turns out to be lower than 40 MeV.cm2/mg, then a decision is to be taken

according to the cross section of the device and its system criticality. As it is

not easy to perform tests at both facilities, it has been suggested to perform

combined protons and heavy ions tests only on the most risky components.

o Another approach has also been proposed, which consist on performing tests

at PSI by increasing the design fluence to enhance the statistics. However the

limitation of this method is that the TID will also increase. Mitigation

techniques at design levels are to take be into account to reduce the risk of

destructive events.

o Degradation due to TID and DD (impact only on a subcategory of

components) will appear at a later stage in LHC operation, but is likely to

affect many parts at the same time. Thus, TID tests cannot be neglected for

parts installed in the tunnel (details on the radiation levels are given by area).

However, maintenance can be foreseen but requires adequate radiation

monitoring and good knowledge of the life-time limits of the used components

(including an inventory in case various batches/producers of COTS are used),

thus an assurance on this task remains the responsibility of the respective

equipment group.

o As an alternative, margin factors on the target limits can be taken, however,

while they are acceptable for the ARC they will be limiting for certain DS

locations. Optimization measures are thus possible:

According to the TID levels expected in the ARC tunnel, where most of

the electronic is placed, the reviewers tend to judge the radiation

cumulative effects as a second order problem with respect to the

destructive events. Signals can be monitored to verify the status of the

board, provided that the equipment group takes care of this aspect in

the design phase (automatic reading of test points, e.g. the monitoring

of the power consumption drift due to the TID).

A regular exchange program between more and less exposed areas is

recommended to lengthen the overall life-time of systems.

A safety factor of 3 is understood as being correct for ELDRS (affect

only bjt, bipolar, bicmos). However, it can be optimized according to the

type of the component to test. Random tests of entire boards should be

used in the qualification process even though maximum quality

assurance on the components is compromised.

- Given the amount of components to be used in the power-converter design, the

question concerning required series test of components for each lot (tunnel

equipment) has to be evaluated with respect to the corresponding effective risk:

o Concerning cumulative damage (TID, DD), both necessity and optimization

options where discussed, including the option of “over-tests” (e.g. the test is

carried out at x10 the TID target [n=5 samples, N(lot) 1000]; if the test is

successful, the lot can be accepted assuming that the spread among samples

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will not be higher than one order of magnitude), however the right choice of „n‟

has to be clarified. 5 samples for a large quantity of parts (e.g. 1000) is

commented as a small sampling size. Instead of using an arbitrary margin of

5 or 10, the use of a statistical analysis is recommended (see MIL-HDBK-814)

o Also, one thing to consider is the radiation source that you use to perform TID

tests. Is it a worst case for the environment?

o “TID over-tests” can be applied for the test of component lots. Electrical

parameters (VBDS for a MOSFET, VBCE for BJT) have to be measured to

select the most representative samples. However, later control tests of entire

boards are considered as a good trade-off to allow for a faster qualification

process.

o For destructive SEEs both the risk and the impact on operation is higher

questioning spread among lots and different lots. For soft SEEs, this is

considered less of an issue if correctly taken into account at the design stage.

“Over-test” is in this case not an option and only sufficient statistics can

provide a definite answer. It‟s thus important to correctly choose the number

of samples to test a lot, still by keeping the test effort reasonable.

o Neutron tests could be useful to reach high fluences without degradation of

the device (TID). However, the reviewers warn that it is difficult to find a good

definition of a „lot‟ for commercial component, in which case one has to test

devices from the same lot and see the variability of the requirements.

Literature reports that batch variations affect especially TID effects, while for

SEEs it is only critical for destructive events. ESA generally works through

procurement lots, using package marking information (date code) as well as

die marking on a sample of the devices. Based on this a statistically sufficient

number of parts to test is defined. Sometimes additional information can be

obtained from manufacturer.

o One additional option is to propose to the manufacturers paying a higher price

per component if the manufacturer can assure that all the parts come from the

same lot. This is considered as a possibility for a significant volume (financial),

will however remain difficult and has to be evaluated on a case-by-case basis.

In general, it can be concluded that one shouldn‟t stress too much the

importance of ELDRS since only a fraction of components (families) is

affected. Moreover, radiation tests performed at real tunnel dose rate are

impossible to do and other tests will give only partial results. The reviewers

recommend that test points on the boards are added to allow following the

degradation of the devices, e.g. the monitoring of the power consumption drift

due to the TID. The return of experience is underlined as very important to

indicate if one is doing too much or not enough in this area, thus the

importance of monitoring radiation environments around your equipments.

o It is important to note that (existing) neutron test facilities are used especially

for ground test, thus the respective flux being low (in the >100MeV range).

That implies spending a lot of time to get statistics. A CERN test facility with

sufficient fluence and better neutron/dose ratios would be a good option, at

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the same time also interesting not only for CERN experimental groups, but

also the aviation/train and car community (RadSol).

o It is agreed that adding margin factor on the target fluence is the only way to

sufficiently qualify a lot. If this is not possible due to fluence/dose limitations

during the test program, provided that a screening test was done on the

components, a control through series tests can be done on entire boards. It

has been suggested that for the test of the equipment cards, a selection of

boards can be selected and tested to get a distribution (assuming that the

tested population is representative of the lot). See also respective comments

above (ESA).

o For new designs in the accelerator sector (QPS, power-converters) it has

been strongly proposed to organize regular design reviews between

equipment owners and internal/external experts in order to evaluate the

various design stages, but also optimize the process by verifying if there are

additional design options to solve easily some issues.

- Availability of test facilities: due to the limited access to PSI, the known limitation of

CNRAD (including the fact that operation beyond 2012 is not guaranteed), all

reviewers agree that a new test facility is required in order to assure the test

requirements from the accelerator sector. Based on the presented first design study

and combining the requirements from both the experiments and the machine, the

suggested facility in the East-Area (EAIRRAD) is considered as the best solution,

however would require its implementation during LS1. It‟s important to note that

neutron fields in the respective energy range and also including thermal neutrons are

of interest also outside CERN (aviation, train & car industry and respective research

activities for radiation damage issues – RadSol community).

- As already performed in 2011, the use of external companies to test specified

components was discussed. Respective specifications must be very clear and the

support needed to specify the test requirements is not to be underestimated. The

reviewers strongly recommend that a CERN member should join the test campaign.

It is very important to establish a good statement of work form beginning. The

recommended approach is that a detailed test plan is available prior the tests. This

being said for the SEE test of unknown parts, it is impossible to foresee everything in

a test plan. This is why it is important to attend and lead the SEE test campaigns

even when one subcontracts a SEE test. For TID or DD if it is on a particle

accelerator, it is also better to attend. Also for the equipments designed in house; it

is very important to involve the designers in the tests.

- A further iteration with ESA is suggested to better understand what procedures are

to be used to work with external companies.

- The analysis of machine failures due to radiations was discussed. All reviewers

agree that the information is crucial to follow-up the failures. The support by the

single equipment groups is fundamental. Equipment groups should include the

option of "failure due to radiation" in their database and interact through the RadWG.

However, it will remain difficult to take into account failures which did not (or not

sufficiently often) appear yet. Those add an additional uncertainty to the forecast for

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the following years. Regarding the next year, the machine operation should not

increase a lot the radiation levels measured in 2011. A factor of about 3 is taken into

account before LS1 when many systems will be relocated into safe locations. Similar

resources as in 2011 shall remain available to follow closely the LHC operation and

failures to be iterated with the respective equipment owners.

- Failures forecasts are required for the following years based on (i) the expected

radiation levels, (ii) past observed failures, and (iii) performed mitigation actions. The

reviewers pointed out that it‟s important to define a failure budget for each equipment

owner. The downtime for the LHC operation is then indicated as a figure of merit,

where for evaluating the latter, the EN/STI group can provide cross section of the

equipment that have been tested (or based on observed failures in the machine).

However, it‟s the responsibility of the equipment owner to compute what it means in

terms of failure rate according to the number of their systems and the radiation levels

in respective LHC areas. Through the R2E project and the RadWG a maximum

allowable time loss per week could be defined for all exposed equipment together (in

agreement to the operation), then allowing to link each equipment failure to an

average downtime (to be evaluated). It is suggested to start from the systems whose

failures along 2011 are better known.

- Concerning failures of entire system the possibility of a detailed analysis depends on

the system itself and on the knowledge of its parts. The reviewers advise to test the

entire system whenever possible, however including additional monitoring

capabilities which have to be part of the system design

- Patch solutions are obviously very effective and often have to be anticipated before

radiation testing becomes possible. For the power converted redesign a first

emphasis must be put on the AC-DC failure and will be addressed during the early

months of 2012. For the QPS system firmware and hardware upgrades are foreseen

for the Christmas break. However, due to time constraints, the hardware upgrade will

be done by partly using components which are known to be radiation tolerant but

where the quality assurance cannot be maintained for on the component

procurement. The reviewers suggest that tests of the cards are performed in parallel

in order to have a parallel cross-check allowing to spot possible hidden problems.

- The reviewers agree that mitigation actions can be very effective. The single cases

cannot be judged by the reviewers since a detailed knowledge of the system is

required. However, the equipment groups being responsible for their systems are

invited to organise reviews also for the patch design and seek support and feedback

through CERN internal and external channels.

- Simultaneous testing of effects (TID, DD, SEE) is considered as a good compromise

for LHC applications. Pulsed fields (e.g. CNRAD) even with rather short pulses

(10ms in the case of CNRAD) remain acceptable if for instance discrete fluences are

not exceeding 107-109cm-2 per pulse – it‟s important to note that results are likely to

be conservative.

- For IGBT devices the reviewers underlined that between lots (e.g. lot of 100 in one

case) large differences can be observed (e.g. three decades), respective quality

checks (or sufficient sampling) are thus considered as important. One reviewer noted

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in addition that it‟s important to clarify if the tests were done covering a voltage range

large enough to make sure that the IGBTs were not measured on the highest slope

of the cross section curve. It is suggested to monitor in detail the voltage at which the

cross section is saturated without limiting the test at the 50% of the maximum rated

voltage breakdown.

Page 15

Session – 3: Power-Converter Radiation Tolerant Development & Super-Conducting

Links

One year after the decision was taken to start through the R2E mitigation project with a

radiation tolerant design for the LHC power-converters, a strategy and planning has been

developed on how to organize the power-converter and respective control development, the

radiation testing and the system design. The corresponding requirements were put in

perspective to the observed failures during 2011 LHC operation as well as the test results

obtained at H4IRRAD. Super-Conducting links being a solution first studied for the LHC

upgrade scenarios (requiring long vertical links) are considered as an additional mitigation

option for the power-converters. Given the fact that most likely all power-converters

installed in the UJs will have been relocated to „radiation safe‟ areas after the next long

shutdown, the remaining converters installed in the RRs where any relocation requires

either a radiation tolerant design or a new solution of long super-conducting links, to be

integrated together with their cooling station and connections. While the requirements for

the upgrade scenarios are in a more distant future, the possible application of super-

conducting links to the existing power-converters led to an advanced test study of technical

solutions for both, horizontal and vertical links.

Identified follow-up actions:

- The destructive events on the 600A AC/DC shall be analysed through tests at PSI in

order to identify the weak component(s).

- The development of the FGClite shall be pursued with high priority, aiming for first

production batches to be ready towards the end of LS1.

- Design reviews shall be organised for the different parts of the power-converters

from the very beginning onwards, including the analysis of test procedures and

mitigation measures to be considered during the design phase.

- Internal and external possibilities are to be investigated in order to detach a radiation

test expert for the next two years to support upcoming CERN test campaigns.

- Based on the existing preliminary design study, the possibility to build and run PS-

EA-IRRAD after LS1 should be investigated with high priority.

- The integration study for super-conducting links, as well as civil engineering pre-

studies are to be continued/launched with high priorities: scheduling and cost

estimates shall be reviewed by 2012/13.

- Investigate the option to power certain orbit correctors with 60A converters.

- Radiation test results shall be well documented and made easily available to the

entire community.

The main conclusions are summarized as:

- LHC 600A – 10V: 8 Destructive SEL on AC/DC. Not clear which component is

responsible since several were burned. Need to be addressed especially for after

LS1.

Recommendation: try to test the card in PSI to identify the weak component.

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- FGC Controller: Some failure modes encountered during LHC operation and

H4IRRAD tests could be successfully mitigated by firmware updates. 2012 operation

will not be significantly affected. As soon average radiation levels in the ARC (high

number of exposed FGC units) will increase, counter-measures through patches risk

still to affect LHC operation. The suggested FGClite development is approved as an

efficient and effective mitigation measure.

Recommendation: pursue FGClite development with high priority, aiming for first

production batches to be ready towards the end of LS1.

- For all new converters: Not clear that it is really possible/useful to test all the

components. Different solutions may be investigated (see also reviewer comments in

Session-2), e.g. select critical components that have to be tested and be absolutely

guaranteed not to suffer for SEL, and other that may eventually be prone to failures

caused by radiation, and mitigate the failure by redundancy or other measures. Card

and system tests (with sufficient number) performed in parallel to the

design/development can then be used to verify possible additional weaknesses.

Final system tests are used to certify an overall acceptable MTBF.

Recommendation: Organise Design Reviews of the different designs to identify

components to be tested and components to be duplicated or triplicated. Try to

identify as well alternative design to reduce testing needs. Whenever possible try

purchasing single batches only (higher prices can be accepted and enable

manufacturers/distributers in some cases to provide them).

- Test and design: EPC team will be reinforced. STI team needs to be reinforced

Recommendation: Seek internal and external possibilities to detach a radiation test

expert for the next two years to support upcoming CERN test campaigns.

- Test Facilities: To be sure about Latch-up foresee test with Heavy Ions. For other

tests and respective CERN constraints the point was raised if present CERN

internal and external facilities are sufficient. It was agreed that we should try to have

a facility with sufficient fluence at CERN. PS-East-Area seems the best candidate.

H4Irrad is limited in fluence, CNRAD is fully parasitic and probably will close in 2012.

Recommendation: based on the existing preliminary design study investigate

possibility to build and run PS-EA-IRRAD in LS1.

- Superconducting Links:

Recommendations:

o Complete integration study as soon as possible

o Study how to support the vertical links

o Define civil engineering studies to be performed and launch them

o Study installation procedures and schedule. Define what can be done in LS2

also in view of LS3.

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- The 60 A power converters need to be radiation tolerant and should cope with the

radiation dose that is expected for the long term future (incl. luminosity upgrade). It is

not conceivable to power the orbit corrector magnet from areas that are free from

radiation.

- Until 2012/13 a global view is required addressing the following questions:

o What is a realistic schedule and cost estimate for the installation of super-

conducting links and in what areas?

o How many power converters must remain in areas with radiation (as for the

60 A converters)?

o What is the expected MTBF due to radiation for those converters that would

remain in radiation areas for some limited time?

o The number of types of radiation tolerant power converters should be

optimized, with the development of a radiation tolerant FGCs as top priority.

- Power converters for 120 A: the reviewers raised the question if a number of these

converters might operate with a current of less than 60 A, since operation does not

required higher current. Could 60 A converters be used for such circuits? Could two

60 A converters be coupled to provide 120 A?

- The reviewers raised the question of documentation of the radiation tests: when

components are radiation tested, the knowledge of the tests as well as the test

equipment should be available to all CERN teams working on radiation tolerant

electronics. CERN equipment teams should be involved in the testing.

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Session – 4: Integration, Implementation, Planning & Safety

During the past year a lot of work has been performed preparing (and partly implementing)

R2E mitigation actions for shielding and relocation. Shielding activities will involve the

installation of several hundred tons of both iron and concrete blocks, involving respective

layout studies and optimizations, purchase, preparation and logistics. Relocation activities

impact a large number of equipment groups and partly important space constraints have to

be considered including respective cabling requirements. An important amount of work has

been performed leading us towards complete integration solutions for almost all critical

areas where shielding and relocation measures have to be taken. Besides the actual

solution finding, all areas were entirely revised to assure first a coherent „as-built‟ situation,

then allowing a coherent implementation of the envisaged mitigation actions which will

become one of the key issue for the actual implementation work to be carried out

throughout the upcoming xMasBreak and the long-shutdown in 2013/14. The status of all

activities (integration and implementation) including the already well advanced planning

studies has been reviewed.

Identified follow-up actions:

- Safe-room constraints and proposed solutions (even if temporary and requiring

compensatory measures) have to be clarified by January 2012 – (EN/DSO, EN/EL,

GS/SE, GS/ASE and R2E follow this with high priority)

- Civil-engineering pre-studies for the SCL implementation of the RRs at P1/5 shall be

started already in 2012, including geological test drillings.

- For the TZ76 wall dismantling (including the ventilation ducts) a cost and resource

estimate is to be performed (GS/SE) for both options: (1) 50m (required for R2E), (2)

full remaining length (preferred solution for the long-term).

- Optional work in two shifts (EN/EL) also for Point-1 is to be investigated in order to

gain margin for the cabling activities.

- Work between and availability of involved design offices must be assured during

early 2012 in order to remain within the required preparation deadlines.

- Point-7 integration, implementation and planning considered as most critical due to

the shorter time available for mitigation measures during LS1 (8 months) –

respective integration and implementation studies (including planning) are to be

followed with high priority after the clarification of the safe-room issues (including all

required services)

- Resources required for worksite supervision and coordination are to be allocated

already in the second half of 2012.

- Purchase procedures are to be launched even if not all input is available, but which

can be added later to the tendering and final order.

- Storage constraints (surface and tunnel) have to be addressed and coordinated

between all LS1 activities. Respective requirements should be ideally coordinated

and formalized through a dedicated tool.

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The main conclusions are summarized as:

LHC Point-7:

- Integration studies for LS1: the main concern is to finish by March 2012 the

integration and planning studies for the Point 7 relocations. Today the integration

study is in stand-by as a solution has to be found for the relocation of the EN/EL

equipment located in the UJ76 safe room and to be relocated in the TZ76 gallery.

Due to space constraints a safe room as in its present configuration cannot be

implemented in the TZ76 gallery. A technical solution which meets the safety

requirements (i.e. especially resist 2 hours to fire) has to be found by the end of the

year until early January. This is a blocking point that will delay the overall preparatory

process if not solved in time. It was agreed that a small team will review the options

for TZ76 (DSO, EN/EL, GS/SE, GS/ASE, R2E) with the requirement to agree on a

solution together with HSE by January 2012 („best possible‟ and possibly to be

complemented with compensatory measures if required). HSE agreed to provide

support for the fire accident scenarios through an external consultant and respective

analysis, also in order to allow defining compensatory methods if required.

- TZ76 wall dismantling: the TZ76 separation wall needs to be dismantled during

LS1 along 50 m to allow the relocation of racks from UJ76. This activity will be

supervised by GS/SE. In view of the future projects to be implemented in this area

after LS1, it is proposed to dismantle during LS1 the entire wall along 235 m. J.

Crespo (GS/SE) will provide the cost estimates of both options by December 2011

(including also the required dismantling of the ventilation ducts). The R2E project will

then submit this proposal to the management underlining the benefits and

constraints in terms of planning and costs, future upgrade requirements and

protection of the equipment already installed in TZ76 (dust).

Civil engineering for superconducting link (SCL):

- The preferred solution is to drill ducts from surface to RR caverns to allow for the

installation of super-conducting links. In order to respect permit and tendering

delays, the decision for implementation has to be taken by December 2013. The final

drilling (connection) can be performed only with the RRs caverns being empty, in

addition it is preferred to perform the entire drilling in one action, thus requiring the

relocation of the RR equipment prior the start of civil engineering actions.

- The duct size is limited to 40cm. Final dimensions of the SCL including the high-

power converters (4/6/8kA) have to be verified.

- Water infiltration by the new ducts must be avoided.

- The removal and re-installation of the equipment in the RRs is likely not to fit in a one

year stop (first rough estimate by K. Foraz) and a more detailed planning has to be

established to more precisely determine what minimal time-span is required. With

the surface building being close to the CERN site boundary, the respective location

shall be reserved as soon as possible (e.g., to avoid interference with new parking

lots at Point-1) and geological studies shall be started in 2012 in order to check for

Page 20

possible limitations and refining cost and time estimates. For the latter, the full costs

shall be taken into account, including surface buildings and services.

- Possible mixing of air between machine and surface areas has to be studied

(assumed as not being a show-stopper). Both integration and planning studies shall

be started during 2012.

LS1 Planning:

- Point 1 activities will last 12.5 months. There is no margin in view of the others LHC

activities to be performed in this area. A margin may be found if EN/EL would work in

a 2 shifts per day basis. A new iteration should be performed if needed.

- Point 5 activities will last 13.5 months (with 2 shifts per day for EN/EL and civil

engineering teams). There is only 1 month margin.

- Point 7 planning is in preparation. It has to be finalised during March 2012. Its status

depends on the status of the integration study. In LS1, the powering tests will start by

sector 6-7 in October 2013. This implies that Point 7 has the least available time for

activities (8 months).

- Point 8 activities will last 6 months. A lot of activities have been anticipated in 2011.

This planning may be reviewed in view of the manpower requests in Points 1 and 5.

Resources and manpower:

- General: the R2E planning will be merged with the overall LS1 planning to identify

potential issues/problems. Today the manpower for radiation protection is not

included.

- Integration: 5 different design offices are involved in the R2E integration studies

with their own priorities on different projects. This generates time delay. Synergy and

common simultaneous effort is needed to finish Point 7 integration by March 2012.

- EN/CV & EN/EL: even if today the manpower estimate for R2E activities is defined,

the availability for R2E will be decided later according to priorities of all activities to

be performed during LS1.

- Coordination & follow-up: the required resources are today defined for each year.

The reviewers comment that worksite supervision will be crucial and should not be

underestimated (2 or 3 FTE to be confirmed), both on the overall R2E coordination,

as well as the service and equipment groups. These persons have to be identified

and they are needed already in 2012 on a part time basis.

Organisational aspects:

- Material procurement: all the material requirements are today well defined. The

remaining purchases have to be launched as soon as possible in view of the

installation periods to avoid delay during LS1. R2E tendering procedures are partly

linked to other projects/activities in terms of material orders (e.g. water cooled

cables). This may lead to delay in the ordering process, thus the equipment that may

be impacted has to be identified. Tendering procedures should thus be launched

already now, keeping the detailed quantities open until the final order.

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- Storage: The advance delivery of few months may generate the needs of storage

areas in surface. In the same way, available space underground is even more

constrained and clear procedures are required in order to avoid respective work

delays. Both aspects have to be taken into account during the coming months of

preparations, both within the R2E implementation work, but also on a global LHC

shutdown basis.

- General coordination: in view of the work load in Point 5 (2 shifts per days for

EN/EL and GS/SE teams), facilities (as canteen) should be installed in Point 5 to

avoid loss of time. The procedures for the transport of material have to be made in

advance. A detailed planning of the underground and surface storage areas has to

be prepared.

- Safety: the procedures will be written by the technical persons in charge. A precise

list of the required procedures is needed. The installation of shielding walls should

take into account the He path.

- Access: of people should be optimized to avoid loss of time.

Additional remarks:

- The (air) leak tightness of ducts and overpressure schemes must be maintained.

- The reviewers pointed out that no resources are available (foreseen) for crisis

management. This together with the little margin poses a significant risk of delays.

Page 22

Session – 5: Resources & Strategy

Also based on the previous technical sessions this last session aimed at three main

aspects: (1) a focus on the R2E related planning and resource requirements, (2) a review of

the required radiation test and monitoring requirements and (3) an update of the overall

R2E strategy and priorities for the coming years. It was discussed whether our radiation test

resources are sufficient and what further optimization is possible in terms of: outsourcing of

test activities, availability of test areas and test procedures. In this context also the

continued need of radiation monitoring for electronics and the development of a 2nd

generation RadMon was agreed upon. The complete list of mitigation actions (shielding,

relocation and new developments) were addressed and verified how to fit best into the LHC

planning constraints. Additional flexibilities are required (e.g., in case certain planning

constraints change or delays/problems appear (plan-B)) especially important for critical

activities (cabling, cooling and ventilation). The latter have to be addressed through careful

preparations and procedural planning. The current safe-room situation and respective

global CERN review remains a blocking point for the finalization of R2E mitigation studies

and a high-priority follow-up program was agreed upon. The status of the R&D of radiation

tolerant power-converters was summarized together with the update on the super-

conducting links, confirming the combined strategy as foreseen in the R2E mitigation plan.

The main conclusions and follow-up actions:

LHC Point-7:

- Radiation test resources: PS-EA-IRRAD integration and implementation study to

be launched aiming for an implementation during LS1; additional resources to be

identified (a second test team) in EN/STI

- Safe Room: nominate Owner & Consolidation Project Leader. Prepare a technical

specification of the safe rooms as they will be consolidated at the LS2 horizon in

order to obtain a set of derogation measures for the present temporary consolidation

programme. Person to be identified in the Sectorial Safety Unit or … EN.

- Shielding & Relocation: review resources for coordination of installation of

shielding

- Cables & Fibres: resources required for R2E and other LS1 activities too many for

CF supervision: arbitration by R2E & LS1 projects.

- Dilemma: invest in the SC link or Power Converter redesign? A mix of both. For

the PC : FGC light & 600A 10V redesign are highest priority. 4 posts in EPC already

published.

- Superconducting Link: It is fundamental for LHC beyond LS2. CERN must launch

a study and a project including forages, quench protection and the mechanical

support of the cable inside the cryostat as well as the cable inside the hole in the

ground. A mature design must be ready for LS2 in view of a first horizontal

installation in Point 7 and a potential vertical SC link.

- Planning:

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o studies for Point 7 must be rapidly completed to give the green light before the

end of year for the integration.

o approve the complete demolition of the wall separating the technical gallery in

TZ76 : verify with the planning of LS1.

o budgets must be consolidated and verified to be inside the MTP figures.

o Ensure the involvement of the support groups.

o Prepare alternative strategy and plan for R2E consolidation if found short of

time during LS1.

- Procurement Procedures & Contracts: must be launched even if uncertainties

remain:

o foresee options in the contracts.

o include possibility of two shifts for all support contracts foreseen for LS1, in

particular for EN-EL

- Logistics: storage space (both surface and underground) management in

preparation for and during LS1: feedback after review summary – EN/MEF/LPC in

charge

Page 24

External Reviewers for the first three technical sessions:

• University of Montpellier (IES): one of the leading university in France (Europe) with respect to radiation damage, long-lasting experience in satellite missions

– Dr. Frederic Saigné (group leader)

– Dr. Frederic Wrobel (Single-Effect modelling, testing and calculations)

– Dr. Antoine Touboul (expert for radiation effects on power-components, especially destructive ones caused by atmospheric neutrons)

• ESA/ESTEC: responsible for all European space missions, ESTEC being involved in radiation tests, standards and all related mission activities including radiation monitoring & calibration

– Dr. Christian Poivey (SEE Standards)

– Dr. Giovanni Santin (Modelling & Calculations)

• One of the European „Gurus‟ for radiation damage to electronics.

– Dr. R. Gaillard (IEEE Senior Member & Consultant)

Internal Reviewers:

F. Bordry (CERN/TE): TE Department Head

J. Christiansen (CENR/PH): PH-ESE Group Leader (electronics systems for

experiments) and expert on radiation damage to electronics

D. Duret (CERN/TE): TE Departmental Planning Officer

F. Faccio (CERN/PH): Long-year expert on radiation damage to electronics

P. Farthouat (CERN/PH): PH-ESE GL deputy, Frond-End Systems Section Leader

and expert on radiation damage to electronics

A. Ferrari (CERN/EN): CERN FLUKA-Team leader, main author of the FLUKA code

K. Foraz (CERN/EN): Planning & Coordination section leader

F. Formenti (CERN/TE): TE Electronics Coordinator

G. Mornacchi (CERN/PH): Group Leader of ATLAS detector operation and expert

on Monte-Carlo calculations

M. Nonis (CERN/EN): Cooling & Ventilation Group Leader

J. Pedersen (CERN/EN): EN Departmental Safety Officer

S. Prodon (CERN/EN): EN Departmental Planning Officer

S. Roesler (CERN/DGS): Radiation protection section leader for accelerator and

sites, FLUKA author and Monte-Carlo calculation expert

R. Schmidt (CERN/TE): Machine protection expert and deputy group leader

S. Weisz (CERN/DG): CERN Project Office and LHC expert

The review organisers, session chairs, secretaries and speakers as well as the R2E

project leader would like to express their sincere gratitude for the help of the

reviewers.

Page 25

APPENDIX

Review Program Overview

Introduction: Aim of the review + Performed Actions

chair: M. Brugger

(Monday Morning, 21.11.)

1. Calculations & Monitoring (Monday Afternoon, 21.11.)

chair: M. Calviani

reviewers: A. Ferrari (CERN/EN), G. Mornacchi (CERN/PH),

S. Roesler (CERN/DGS), G. Santin (ESA/ESTEC), F. Wrobel (ISE)

secretary: R.A. Garcia

2. Radiation Testing, Equipment Failures (Tuesday Morning, 22.11.)

chair: G. Spiezia

reviewers: J. Christiansen (CENR/PH), F. Faccio (CERN/PH),

P. Farthouat (CERN/PH), R. Gaillard (Consultant),

C. Poivey (ESA/ESTEC), F. Saigné (IES)

secretary: J. Mekki

3. Power-Converter Radiation Tolerant Development & Super-Conducting Links

(Tuesday Afternoon, 22.11.)

chair: R. Losito

reviewers: J. Christiansen (CENR/PH), F. Faccio (CERN/PH),

F. Formenti (CERN/TE), R. Gaillard (Consultant),

C. Poivey (ESA/ESTEC), R. Schmidt (CERN/TE),

A. Touboul (IES)

secretary: Q. King

4. Integration, Implementations, Planning & Safety

(Wednesday Morning, 23.11.)

chair: A.L. Perrot

reviewers: K. Foraz (CERN/EN), M. Nonis (CERN/EN),

J. Pedersen (CERN/EN), S. Roesler (CERN/DGS)

secretary: S. Baird

5. Resources & Strategy (Thursday Morning, 24.11.)

chair: R. Saban

reviewers: F. Bordry (CERN/TE), D. Duret (CERN/TE),

S. Prodon (CERN/EN), S. Weisz (CERN/DG)

secretary: M. Brugger

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Condensed R2E Introduction/History:

The following paragraphs aim to briefly summarize the general points (and recent history)

important for all „Radiation To Electronics (R2E)‟ activities around the LHC:

- The CNGS incident in 2007 triggered a review of radiation levels around LHC

underground areas and installed equipment. A study-group was formed leading to

immediate short-term actions (e.g., shielding) and a first proposal towards a

mid/long-term strategy (see e.g., Chamonix 2009 and Mitigation Proposal)

- With the start of LHC operation, an important effort of FLUKA Monte-Carlo

calculations to predict radiation levels, improved monitoring and respective

calibrations (e.g. for the LHC RadMon system, see e.g., RadMon Mini-Workshop)

and early evaluations through dedicated benchmark measurements, as well as LHC

in-situ measurements, soon allowed for a rather complete inventory of critical areas

and their expected radiation levels (see LHC area overview: past and present)

- Installed equipment ranging from CERN internal (partly radiation-tolerant) design to

fully commercial systems with unknown radiation tolerance, required a detailed

analysis of respective failure risks, triggered radiation test campaigns (themselves

requiring adequate and available test areas, e.g. CNRAD) and a change in the

organizational structure of how radiation induced risks to electronics are followed in

the CERN accelerator sector (see: R2E school and related report, RadWG, R2E)

- This together with additional short-term improvements (mainly shielding)

implemented in the LHC, allowed then to continue the detailed analysis in all

required areas: radiation levels and monitoring, radiation tests and analysis of

failures, study and analysis of possible mitigation measures (see e.g. papers and

presentations of the dedicated session in Chamonix 2010: R2E Overview

[paper/presentation], Equipment Overview [paper/presentation], Radiation Tests

[paper/presentation] and Summary [paper/presentation]

- For most of the equipment shielding and relocation options soon became attractive

as the best long-term approach for a number of critical areas (given the fact that

most of the concerned systems are purely commercial, thus also prone to changes

over the LHC life-time). However, for the LHC Power-Converters this approach could

only be followed for parts of the areas (low-voltage/high-power puts significant

constraints on how far the converters can be relocated to). Large civil-engineering

activities implying long delays and downtimes, as well as the need to understand in

more detail the possible impact of radiation induced failures, led to the question if a

new radiation tolerant design could become an option for both, the actual mitigation

of radiation failures, as well as a new design of power-converters (see

Internal/External Power-Converter Review (see program, report, EDMS).

- Exploring in more detail the available mitigation options and requirements (see

dedicated R2E Workshop in 2010: program and minutes) allowed agreeing on a

mitigation plan (see LMC summary) and led to the creation of the R2E mitigation

project

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- Focusing on the mid-term mitigation measures (relocation/shielding) required a

detailed inventory of equipment installed in critical areas (LHC Point-1, LHC-Point-5,

LHC-Point-7, LHC-Point-8) and the start of consecutive implementation studies.

- In parallel, along increasing LHC intensity and putting the focus on the detailed

analysis of radiation levels as measured during early operation, a comparison with

observed equipment failures confirmed the proposed R2E mitigation strategy and

allowed to refine the requirements in terms of layout options, timing with a first look

on required resources (see Chamonix 2011: Integration and Implementation, R2E

Project Report)

- The LHC Power-Converters being a key-player for the mitigation measures and to

define the R&D requirements for their new radiation-tolerant development required

the creation of an adapted radiation test area (see H4IRRAD), successfully operated

along the year and allowing to confirm LHC observations throughout 2011

- The recent emphasis now being on the optimization process (e.g., putting on hold

the installation of additional collimators in IR3: see respective review) and how to

choose/refine the best strategy of mitigation measures and corresponding activities

(see the website for Integration & Implementation, various seminars and overview

presentations: R2E Project Overview and PH/ESE Seminar, TWEPP 2011) led to the

organization of this R2E review (see program)

- Furthermore, for all critical areas requiring shielding and/or relocation actions,

detailed integration and implementation studies were performed and are close to be

ready for approval. In parallel, the work on the planning integration has already well

advanced. Both crucial for the success of the R2E project, the coming months will

imply critical decisions in order to guarantee that the work can be started in time

(beginning of LS1) and all parts are optimized the best possible way in order to

assure that the shutdown length can be kept (see the website for Integration &

Implementation).

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Radiation Levels Summary:

During the reviews a radiation level overview (for nominal/ultimate LHC conditions) was

discussed and distributed. While a detailed analysis is discussed in various publications

and past presentations, details area also available on the R2E website (see direct link) and

briefly summarized in the following table: