CTF3 Drive Beam studies results & Program Piotr Skowroński for the CTF3 team 30 December 2013 CLIC Workshop

Factor 4 recombined beam Routine 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 2013 CLIC Workshop

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 2013 CLIC Workshop the Stretcher (Frascati Chicane) ―2011 ―2012 BPIs Tobias Persson

Orbit issues There 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 wall The reasons are continuously investigated  Several alignment campaigns done  Magnet checks  Improvements are clear, but still the situation is not fully satisfactory Using the magnetics correctors bluntly leads to spurious dispersion and eventually to losses Plan to use more sophisticated beam based steering over all of the lines  Variant of Dispersion Free Steering that targets nominal dispersion pattern 30 December 2013 CLIC Workshop

CR recombination with new attenuator for the 2 nd RF deflector Closure within 1mm 30 December 2013 CLIC Workshop (BPI charging up) (not real) RF bump

Dispersion The dispersion is well controlled Need to be careful with strong steerers which can spoil dispersion Controlled 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 2013 CLIC Workshop Horoizontal BPM/BPI traces along pulse with energy step Lower Energy Higher Energy Lower Energy Higher Energy Vertical Bad BPI

30 December 2013 CLIC Workshop Factor 4 recombined beam Emittance in mm mrad LINAC Girder 10 Horizontal: 40-> 60 Vertical 40 -> 60 CLEX Entrance Horizontal: 170-> 350 Vertical 125 -> 200 CR Extraction Horizontal: 75-> 150 (?) Vertical 37 -> 100 (?) Behind Stretcher Horizontal: 60-> 90 Vertical 40 -> 80 CTS Horizontal: 60-> 90 Vertical 40 -> 80

Emittance issues Emittance growth over TL1 and CR The 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 2013 CLIC Workshop

Emittance Studies Influence 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 2013 CLIC Workshop Simulations by Javier Barranco turn 3 turn 2 turn 1 Injection, offset 1mm Emittance growth vs. turn nb. for different injection orbit errors

Emittance Studies Influence 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 2013 CLIC Workshop Simulations by Javier Barranco Measurement by Tobias Persson Emittance vs. orbit error

Transverse mismatch Similarly transverse mismatch leads to the emittance growth through decoherence 30 December 2013 CLIC Workshop 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.

Emittance: the way to go Stability!  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 removal Chromatic 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 commissioned The current one is not symmetric over the cell while sextupoles are connected in series  It would also facilitate fine optimizations of the ring optics 30 December 2013 CLIC Workshop

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 beating Extensive optics measurements were done towards the end of the last run  Ben Constance will summarize his findings in the following presentation 30 December 2013 CLIC Workshop Ben Constance

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 level The biggest issue is the DL orbit closure and its stability  Davide made the automatic tool for that 30 December 2013 CLIC Workshop

Phase Switching Running 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 2013 CLIC Workshop

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 2013 CLIC Workshop

Program Factor 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 TWTs Test 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 deceleration Two-Beam Test Stand (TBTS)  Structures conditioning Two new structures installed last summer Overnight runs  Wake-field monitor tests Both with and without the drive beam  RF pulse shaping tests The dog-leg experiment: break down rates in presence of beam loading Photo gun (PHIN) experiments in CTF2 hall  Requires only one klystron  Last run in 2013 Two-beam modules in December 2013 CLIC Workshop

Phase Feed Forward System 30 December 2013 CLIC Workshop 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 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 CLIC Close link to collaborating partners: INFN-LNF: Phase monitors, strip-line kickers Oxford University/JAI: feedback electronics, amplifiers Phase CTF3 Phase stability 12GHz 1GHz Phase stability 12GHz 1GHz Phase stability 12GHz FONT5 board (Oxford) Stripline kicker (INFN-LNF)

Phase Feed Forward 30 December 2013 CLIC Workshop 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 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 2013 CLIC Workshop 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 comparison Present schedule: Install in winter shutdown Run experiment in 2013

30 December 2013 CLIC Workshop D model of integration of the first CLIC Module in CLEX (2013) CLEX - Three two-beam modules (2014) TBTS PETS tank Module T0 Present schedule: First module installation: end 2013 (At least one year of testing) Module string installation end 2014 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

30 December 2013 CLIC Workshop Schedule 2013 (as of September) Modifications from last month

Schedule 2013 (as of September) 30 December 2013 CLIC Workshop Modifications from last month

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 station Running until all media and services are available Second, 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 year The 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 2013 CLIC Workshop

Known issues and 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 regenerated Not enough man power for this Accepting 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 2013 CLIC Workshop

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 Energy Current Phase 30 December 2013 CLIC Workshop

30 December 2013 CLIC Workshop Modifications from last month