Machine Studies: What did we achieve, what remains to be done and what could be improved?

G. Arduini – AB/ABP

Discussions with S.Baird, R. Garoby, M. Giovannozzi, T. Linnecar, E. Métral, R. Steerenberg, J.-P. Riunaud, F. Ruggiero

are acknowledged

Outline What did we achieve?

An incomplete and preliminary list of results Recommendations issued by the APC Open issues

What could not be done? What was missing? A bit of statistics What could be improved? (a proposal) Summary and conclusions

What did we achieve?(Scrubbing)

Programme defined at the APC:

Accumulate enough dose to study conditioning in cryo-surfaces with 75 and 25 ns spacing and with constant bunch intensity

Signs of scrubbing have been observed in warm and cryogenic surfaces

J.-M. Jimenez

TIME [h]

e-c

loud

sig

nal

[A/m

]

Bunch

popu

lati

on

LHC beam - 75 ns

During the scrubbing run: confirmed the effectiveness of a ceramic insert with resistive coating in reducing the MKQH kicker heating Results and next steps E. Gaxiola in Session 2

What did we achieve?(LHC Proton Injectors)

PS long. coupled-bunch feedback (LCBF) to minimize spread in L available by the end of the 2004 run

LCBF ONLCBF OFF

R. Garoby, J.-L. Vallet

H-transverse instability observed in the very last day of the run when LCBF ON – Working point?

LHC beam - 25 ns

Bunch

length

[n

s]

Bunch number

What did we achieve?(LHC Proton Injectors)

SPS @ 450 GeV/c

As a result of: Modification of the Generators

and PFNs for the “slowest” modules of the injection kicker leading to a reduction of the injection kicker rise-time but not reproducible E. Gaxiola in Session 2

Independent correction of the injection oscillations of each batch

Capture losses: Operation with higher RF

voltage New working point

compatible with larger momentum spread implications for the operation of TFB to be assessed

reduction from 12 to 7-8 % progress in the

understanding but not yet a complete picture need more time to analyze the data

2003 2004

H [m] 2.58 ± 0.45

2.99 ± 0.26

V [m] 4.03 ± 0.17

3.61 ± 0.26

LHC beam - 25 ns

What did we achieve?(LHC Proton Injectors)

PS Reduction of the bunch-by-

bunch intensity spread in the PS

Reduction of the population of the satellite bunches but not yet in a reproducible way

SPS Still problems with the

instrumentation: Bandwidth of the FBCT Instrumental offset in

the horizontal and vertical positions measured by the standard BPMs

Both under investigation U. Raich – Session 2

LHC beam - 75 ns

R. Garoby, S. Hancock

What did we achieve?(LHC Proton Injectors) Produced and accelerated through the whole injector chain Production scheme reviewed (h=1 instead of h=2 in PSB)

it avoids “throwing away” a bunch/ring in the transfer from PSB to PS and it simplifies tuning of the PSB-PS transfer. But this scheme might be limited to nominal intensities (long. instability appearing in the PSB at high energy)

Individual bunch physics and Probe beams

Beam Nbunch

[1011p]

*H/V

[m]

L

[eV s]

#bunches tb [ns]

Probe beam0.05-0.2

0.05< 1

<0.6\<0.3 0.2611

-

Individual bunch physics beam

0.2-1.150.31.1

<3.50.95/0.85<1.8/<1.3

0.40.4

1-4-1616

525525

SPS @ 450 GeV/c

0.01 0.1 110-13

10-12

10-11

10-10

10-9

10-8

10-7

10-6

P [

Tor

r]

Beam time [h]

300 K

77 K

15 K

What did we achieve?(LHC Ions)

Ion desorption experiment at LINAC3 with Pb53+ ions @ 4.2 MeV/u at cryogenic temperatures. Together with the data collected with In49+ @ 158 GeV/u in 2003 encouraging news for LHC although the energy and impact angle dependence up to the LHC conditions is not fully established, yet.

Operation with beam of the LINAC3 stripper and BTV screens at 5 Hz proved that the lifetime of these devices is acceptable for the operation with ions for LHC.

E. Mahner

4.2 MeV/u, Pb53+, = 14 mrad, Cu target

N300 K, 77 K, 15 K = (1 ± 0.2) 109 ions/s

What did we achieve?(LHC test-bed)

LHC prototype collimator tests in the SPS

R.W. Assmann – S. Redaelli

….with some beam left

M. Gasior

Im Z┴ (meas.) ~ Im Z┴ (calc.) !!

Still a lot of data to be analyzed and further studied:

•Tail repopulation after scraping•Exact dependence of the tune shift on the collimator gap

qH coh. ×frev

What did we achieve?(CNGS)

New record intensities in the PS-SPS Complex (~5.3×1013 p/cycle @ 400 GeV/c) see E. Métral, E. Shaposhnikova – Session 3

Vertical aperture in the PS and SPS is critical for minimizing losses at low energy

Importance of careful realignment of the machines (in particular PS and TT2-TT10) recommended by APC and foreseen in the SD planning

Confirmed bottleneck in the vertical aperture in the SPS due to the deformation of the Ti foil covering the graphite core of the SPS beam dump absorber. Need to replace the TIDVG with upgraded one R. Losito – Session 2

Radiation issues need to be clearly addressed for this mode of operation D. Forkel-Wirth, T. Otto – Session 3.

What did we achieve?(CNGS)

Low-intensity double batch extraction to TT40

Demonstration of the feasibility of damping the oscillations induced by the MKE post-kick ripple on the second CNGS circulating batch (back-up solution for intermediate intensities E. Gaxiola – Session 2)

Very promising results from the machine studies for the new PS multi-turn extraction scheme M. Giovannozzi – Session 3.

What did we achieve?(Improvement of operational beam performance)

Change of working point in the PSB major improvements for the TOF and high intensity beams. Need to make a final review of all the observations.

Verification of the feasibility of operating independently the 5 PFW circuits in the PS to provide independent tuning knobs for qH, qV, H, V (presently only 3)

More flexibility for the control of the working point

Implementation of the 5 current mode of operation recommended by the APC as part of the consolidation programme for the PFW power supplies.

R. Steerenberg

M. Chanel

What could not be done? Study the intermediate 25 and 75 ns beams (* vs.

Nbunch) in the SPS. Study the intensity limitations for the LHC beams

(single and multi bunch) up to the ultimate bunch intensity in all the injector chain

Transverse feedback commissioning in the PS

……analyze all the data we collected.

What was missing? Suffered from the poor performance of the WS in

the PSB and PS and frequent wire breakage. Particularly annoying for the studies on the new multi-turn extraction and for the setting-up and qualification of the LHC beams. This went on for the whole run in spite of the complaints. These instruments will be of primary importance for the operation of the LHC beams in the near future.

One SPS WS wire broke during last MD with high intensity beams reason still being investigated.

U. Raich – Session 2

Some statisticsMDs 2004 - TOTAL = 2370 h

PS

675 h

28.5%

PSB &

LI NAC2

291 h

12.3%

LI NAC3

461 h

19.5%

SPS

943 h

39.7%

MDs 2003 - TOTAL=1760 h

SPS

806 h

45.8%

LI NAC3

80 h

4.5%

PSB &

LI NAC2

362 h

20.6%

PS

512 h

29.1 %

Total MD time increased in spite of the difficulties = profit of the “last” SPS run. Large contribution from LINAC3 studies.

Scheduled physics time almost constant (~12000 h in 2003 – ~12400 h in 2004)*

*Total PSB+PS+SPS

Some statisticsMDs 2004 - TOTAL = 2370 h

LHC Proton

I njectors

14.7%LHC- testbed

7.3%

CNGS

20.8%

Setting- up

21.9%

Others

1.1%

TI 8 test

2.9%

LHC I on

I njectors

19.7%

Operation

2.2%

Scrubbing

9.4%

Decreased:

•LHC Proton Injector

•Others

•Operation

MDs 2003 - TOTAL=1760 h

LHC Proton

I njectors

35.2%

CNGS

14.1%

Setting- up

12.1%

Others

4.9%

Scrubbing

11.8%

TT40 Test

2.7%

LHC- testbed

7.5%

Operation

4.2%

LHC

I on I njectors

7.5%

Increased:

•Setting-up time

•CNGS

•LHC Ion Injectors

Some statisticsMDs 2004 - TOTAL = 2370 h

Dedicated

MDs

23.8%

Parallel MDs

76.2%

Scheduled

[hours]

Performed

[hours]

Perf./sche.[%]

Dedicated (TI8 and scrubbing excl.) 376 274 73

Parallel ( LINAC3 excl.) 1416 1345 95

How did we lose time? Higher fault rate in general (PSB delayed start-up and the PS septum problem)

time lost rescheduling required (not always allowing efficient distribution of the MD time)

The absence of an operational beam dump in the PS prevented us to perform MD studies in the PS during the 3 week-stop due to the failure of the PS extraction septum to TT2 Need to provide a reliable beam dump and spare. R. Losito – Session 2.

New timing not fully digested still a matter for a few “experts”

Archiving, interlock handling in the SPS not yet beam oriented SC change requires in the SPS ~1 h with 3-4 persons on deck B. Frammery and B. Puccio – Session 3

Archiving failed in a few occasions (e.g. for the PSB beam for the new CT extraction)

RF settings are often “a world apart”.

A Large variety of beams is required (most of them are not operational, yet) larger dependence on expert availability

What can be done to increase the efficiency of the MDs? (a proposal)

…apart from the (may be) obvious answers: Reduce fault time Minimize number of beams required

The number of “experts” should be increased: Having the operators and shift-leaders responsible for the

performance follow-up (including the beam instrumentation required to measure the beam) and documentation (for the use of the shift crew) of a few beams as a SECOND JOB supervised by the machine supervisors (positive experience for the setting-up of the CNGS beam in the PS and of the pilot beam for the TI8 tests in the SPS)

What can be done to increase the efficiency of the MDs? (a proposal)

How? By dedicating:

more effort (by supervisors and experts) for “hands-on training” of a mini-team of operators this requires at least 1 week in normal hours for each mini-team

part of the machine development and setting-up time for the training

By providing: remote control of ALL the “machine knobs” vital in the new CCC analog signals (also fast ones)

Possible “targets”: LHC commissioning beams (pilot, probe, individual bunch beam)

which will be heavily used for the LHC commissioning and the test beams for the new multi-turn extraction

Summary & conclusions All in all MDs have been rich of new results and

led to a better understanding of the behaviour of the LHC and CNGS beams as well as in testing hardware and operational procedures for the LHC

The portrait here presented is certainly incomplete and preliminary

The recommendations issued by the APC in order to improve the machine performance have been outlined together with the main arguments behind them

Possible suggestions to further improve the efficiency of the machine studies and to create the conditions to make some of the MD beams operational have been sketched