CTF3 Drive Beam studies results &Program

Piotr Skowroński for the CTF3 team

30 December 2013CLIC Workshop 20131

CLIC Workshop 2013

Factor 4 recombined beamRoutine 14A 280ns

CTF3 routinely delivers 14A beam for the experiments in CLEX From injector 4.1 A, ~1200 ns, dE/E 2.5% FWHM After the Stretching chicane: 4 A, 1120ns Extracted from Combiner Ring: 16 A, 280ns

Quality check: recombined pulse stored for few extra turns CLEX: Stable 14 A

It is not certain how much it is a real loss or BPM calibration issue

Measured RF form factors 0.9 – 0.95 Bunch length 17 ps It allowed x4 rep. rate increase to 3.2 Hz

for TBTS night runs

30 December 20132

CLIC Workshop 2013

Losses and Short term Stability (Jitter)

2012 we ran lower R56 optics tails lost in the Stretcher Beam intensity jitter showing off already there Still achieving the same final performance in CLEX

In 2012 the calibration of BPIs and their nonlinearity were corrected still calibration is not 100% certain (see Ben Constance talk )

30 December 20133

the Stretcher(Frascati Chicane) ― 2011

― 2012• BPIs

Tobias Persson

CLIC Workshop 2013

Orbit issuesThere are issues with the orbit at Delay Loop injection and ejection

The beam ends up too low after passing the septa Combiner Ring behind the first bend and in the last arc (horizontal) At the end of TL2 strong steering in horizontal to pass through the

CLEX wallThe reasons are continuously investigated Several alignment campaigns done Magnet checks Improvements are clear, but still the situation is not fully

satisfactoryUsing the magnetics correctors bluntly leads to spurious dispersion and eventually to lossesPlan to use more sophisticated beam based steering over all of the lines Variant of Dispersion Free Steering that targets nominal dispersion

pattern

30 December 20134

CLIC Workshop 2013

CR recombination with new attenuator for the 2nd RF deflector

Closure within 1mm

30 December 20135

(BPI charging up)(not real)RF bump RF bump

CLIC Workshop 2013

DispersionThe dispersion is well controlledNeed to be careful with strong steerers which can spoil dispersionControlled with 2 different measurement methods Scaling all magnetic elements Change of beam energy along the pulse with MKS15 pulse compression

Watch the step in BPM traces

30 December 20136

Horoizontal

BPM/BPI traces along pulse with energy step

Lower EnergyHigher Energy Lower EnergyHigher Energy

Vertical

Bad BPI

CLIC Workshop 2013 30 December 20137

Factor 4 recombined beamEmittance in mm mrad

LINAC Girder 10Horizontal: 40-> 60

Vertical 40 -> 60

CLEX EntranceHorizontal: 170-> 350

Vertical 125 -> 200

CR ExtractionHorizontal: 75-> 150

(?)Vertical 37 -> 100 (?)

Behind StretcherHorizontal: 60-> 90

Vertical 40 -> 80

CTSHorizontal: 60-> 90

Vertical 40 -> 80

CLIC Workshop 2013

Emittance issuesEmittance growth over TL1 and CRThe emittance is blown up with several mechanisms Orbit closure in Combiner Ring Bad orbit Mismatch to the closed CR solution Chroma Non linear dispersion

30 December 20138

CLIC Workshop 2013

Emittance StudiesInfluence of bad orbit on emittance Particles orbitate around fixed point of phase space

It is defined by the magnetic centres of quads If chroma is not corrected (natural negative) particles with higher

momentum rotate slower, with lower momentum – faster Bigger the momentum spread and chroma faster the beam fills up

the phase space: decoherence In CTF3 sigma dp/p ≈ 1%, CR chroma ≈ -13/-9 per turn

30 December 20139

Simulations by Javier Barranco

• turn 3• turn 2• turn 1• Injection, offset 1mm

Emittance growth vs. turn nb. for different injection orbit errors

CLIC Workshop 2013

Emittance StudiesInfluence of bad orbit on emittance Particles orbitate around fixed point of phase space

It is defined by the magnetic centres of quads If chroma is not corrected (natural negative) particles with higher

momentum rotate slower, with lower momentum – faster Bigger the momentum spread and chroma faster the beam fills up

the phase space: decoherence In CTF3 sigma dp/p ≈ 1%, CR chroma ≈ -13 per turn

30 December 201310

Simulations by Javier BarrancoMeasurement by Tobias PerssonEmittance vs. orbit error

CLIC Workshop 2013

Transverse mismatchSimilarly transverse mismatch leads to the emittance growth through decoherence

30 December 201311

Measured beating: Twiss parameters vs number of turns

Simulations by Javier Barranco

• Injection, mismatched Twiss• Turn 1• turn 2 – dumped on closed

Twiss• turn 3

turn no. turn no.

CLIC Workshop 2013

Emittance: the way to goStability! Obviously, if the beam constantly drifts there is no way to optimize it Culprit: the RF pulse compression A lot was done during last year and more will be done, see Tobias

Persson’s talk Hopefully very soon we can concentrate fully on beam optimization rather than keeping the beam in place

More sophisticated automatic orbit correction DFS variant, targeting the model dispersion, i.e. minimize spurious

dispersion Davide Gamba started his contract in January and will take care of it

Automatic orbit closure in Combiner Ring and Delay Loop Davide also will take care of it

Beta beating removalChromatic correction Needs good closed orbit correction first,

Otherwise sextupoles feed-down to quadrupole, change focusing and lead to losses

New optics likely needs to be commissionedThe current one is not symmetric over the cell while sextupoles are connected in series

It would also facilitate fine optimizations of the ring optics30 December 201312

CLIC Workshop 2013

Optics issues

In couple of places disagreements between the model and the measured optics still observed The Stretcher Chicane TL2

Quite large experimental corrections needed to remove beta and dispersion beatingExtensive optics measurements were done towards the end of the last run Ben Constance will summarize his findings in the following

presentation

30 December 201313 Ben Constance

CLIC Workshop 2013

Factor 8

Had it only for couple of weeks in 2012: TWTs problems A spare TWT was ordered in autumn Another spare will be ordered very soon

With 2 TWTs satellites were at 0.6A levelThe biggest issue is the DL orbit closure and its stability Davide made the automatic tool for that

30 December 201314

CLIC Workshop 2013

Phase SwitchingRunning with only 2 TWTs exposed long lasting switching effects which makes factor 8 much more difficult to operate from the start Careful tuning of the low level RF already improved the situation,

but did not remove the effect Will keep looking into this issue Should be minimized with 3 TWTs operational

30 December 201315

CLIC Workshop 2013

Further topics

Several topics are covered in detail in the following talks Status of optics control Bunch length Stability and feedbacks TBL results Profile measurements BPM system status Phase measurements

30 December 201316

CLIC Workshop 2013

Program 2013-2014Factor 8 and experiments with 30A drive beam During this and previous runs fully recombined beam (factor 8)

was available only for short times due to failures of 1.5GHz RF sources

Ordered 2 additional TWTsTest Beam Line (TBL) From 20 A to 30 A, deceleration in the 30%-50% range Dispersion free steering, optics studies

Also extend to high current/large decelerationTwo-Beam Test Stand (TBTS) Structures conditioning

Two new structures installed last summerOvernight runs

Wake-field monitor testsBoth with and without the drive beam

RF pulse shaping testsThe dog-leg experiment: break down rates in presence of beam loadingPhoto gun (PHIN) experiments in CTF2 hall Requires only one klystron Last run in 2013

Two-beam modules in 201430 December 201317

CLIC Workshop 2013

Phase Feed Forward System

30 December 201318 18

Phase monitor

Not just a single experiment – series of related studies: • Measure phase and energy jitter, identify sources,

devise & implement cures, extrapolate to CLIC• Show principle of CLIC fast feed-forward

Fast kickers

Drive beam phase feed-forward concept @ CLIC

Close link to collaborating partners:

INFN-LNF: Phase monitors, strip-line kickersOxford University/JAI: feedback electronics, amplifiers

DRIVE BEAM LINAC

CLEXCLIC Experimental Area

DELAY LOOP

COMBINERRING

10 m

Phase & energy measurement

Fast feed-forward kicker in final

compression line

Phase feed-forward @ CTF3

Phase stability 2.5° @ 12GHz

0.2° @ 1GHz

Phase stability 0.2° @ 12GHz

FONT5 board(Oxford)

Stripline kicker (INFN-

LNF)

CLIC Workshop 2013

Phase Feed Forward

30 December 201319

Phase monitor(INF-LNF, EuCARD)

• Phase monitor tests – 2 monitors installed in summer 2012

• System installation in spring 2013• First system tests planned in

summer 2013

Experiment on the effect of Beam-Loading on Breakdown Rate

30 December 2013CLIC Workshop 201320

•CLEX

• LINAC

• DELAY LOOP

• COMBINER RING

• BL - BDR experiment

From X-band klystron

X-band structure TD24

X-band components

1 A, 240 ns pulse from CTF3 linac

G. Riddone, A. Solodko

Beam loading reduces field locally in the structure ⇨ is it the break-down rate lower (or higher)?• CLEX probe beam has only limited current/pulse length, CLEX Drive

beam has limited rep rate ⇨ use CTF3 drive beam and klystron driven X-band structure

• Reactivate the old ‘30 GHz PETS’ line, 1 A DB current, can reach 50 Hz• Measure BDR with/without beam to get a direct comparisonPresent schedule: Install in winter shutdown 2012-2013

Run experiment in 2013

CLIC Workshop 2013 30 December 201321

3D model of integration of the first CLIC Module in CLEX (2013)

CLEX - Three two-beam modules(2014)

TBTS PETS tankModule T0

Present schedule:First module installation: end

2013(At least one year of testing)Module string installation end

2014

Drive Beam line

Main Beam

line

Two-Beam Modules

CLIC Workshop 2013 30 December 201322

Schedule 2013 (as of September)

Modifications from

last month

CLIC Workshop 2013

Schedule 2013 (as of September)

30 December 201323

Modifications from last month

CLIC Workshop 2013

Schedule 2013

Short winter shutdown: Stop the machine on December 14th and restart operation with beam on

January 21 7 weeks before the LHC stop

Some new equipment will be installed and most of the cabling work will be done

Install demineralizing stationRunning until all media and services are availableSecond, longer shutdown starting end of April till end of July The longer maintenance of the RF system will be done This shutdown may shift later depending on running conditions,

advancement of other activities and readiness of new hardware.CTF3 would restart in August and run until the end of the yearThe dog-leg installation should be completed during May-June, and the beam-loading experiment may start as soon as klystrons 2 to 7 are available.PHIN run also possible in summer, in the shadow of modulator-klystron maintenance of the 2nd half of the CTF3 Linac.

30 December 201324

CLIC Workshop 2013

Known issuesand planned solutions

Demineralized water will not be available from mid-May to mid-August Postpone winter shutdown to May Initial plan: installation of local demineralizing station

Filter cartridges must be periodically regeneratedNot enough man power for thisAccepting to stop for the whole period, still would like to install the system

Access: no operators in CCC/CPS island Moving the control to CSA and to the CTF control room

Possible interruptions of control services Moving some services locally (f.g. ctf3op home directories)

Asking to concentrate all the potentially disrupting interventions, preferably to our summer shutdown

30 December 201325

CLIC Workshop 2013

Conclusion

2012 was very successful Improved the beam stability and quality It allowed increasing repetition rate for over night

TBTS runs Increased over night availability of the drive beam

Still a lot ahead of us Factor 8 with 30A delivered to CLEX Further emittance reduction Stability

EnergyCurrentPhase

30 December 201326

CLIC Workshop 2013 30 December 201327

Modifications from

last month

Modifications from

last month