CTF 3 commissioning status S Bettoni for the

CTF 3 commissioning status S. Bettoni for the CTF 3 commissioning team CTF 3 commissioning status 1

Outline Ø CTF 3 for CLIC Ø Machine commissioning: § § Combiner ring model improvement New lines in operation: o o o Ø 2008 milestones: § § § Ø Factor 4 recombination demonstrated First drive beam in PETS (w/o and w recirculation) First probe beam Bunch length measurement: § § Ø TL 2 TBTS CALIFES RF pickup Coherent diffraction Other topics: § § Steering algorithms Transient compensation Ø The 2009 of CTF 3 Ø Conclusions

CLIC as a multi. Te. V collider Basic features High acceleration gradient (100 MV/m) ü“Compact” collider - overall length @ 3 Te. V 50 km üNormal conducting accelerating structures üHigh acceleration frequency (12 GHz) Drive beam - 100 A, 240 ns from 2. 4 Ge. V to 240 Me. V Two-Beam Acceleration Scheme üCost effective, reliable, efficient üSimple tunnel, no active elements 140 MW üModular, easy energy upgrade in stages Main beam – 1 A, 160 ns from 9 Ge. V to 1. 5 Te. V

CLIC Layout 3 Te. V 326 klystrons 33 MW, 139 ms 326 klystr 33 MW 4. 2 A, 139 mscombiner rings Circumferences delay loop 72. 4 m CR 1 144. 8 m CR 2 434. 3 m drive beam accelerator 2. 38 Ge. V, 1. 0 GHz 1 km eam b n ve Dri eratio gen plex com Delay CR 2 loop CR 1 101 A, 244 ns BDS 2. 75 km BC 2 245 m TA R=120 m , 21. 1 e- main linac , 12 GHz, 100 MV/m km Delay loop CR 2 decelerator, 24 sectors of 878 m BDS 2. 75 km BC 2 IP e+ main linac Main beam booster linac, 9 Ge. V e- injector 2. 4 Ge. V BC 1 ee. PDR DR 365 m 1 km CR 1 48. 4 km eam b n in Ma eratio gen plex com drive beam accelerator 2. 38 Ge. V, 1. 0 GHz e+ e+ PDR DR 365 m e+ injector, 2. 4 Ge. V 245 m TA R=120 m

CTF 3: CLIC R&D Issues – WHERE? Small scale version of the CLIC RF power source üProvide the RF power to test the CLIC accelerating structures and components üFull beam-loading accelerator operation üElectron beam pulse compression and frequency multiplication üSafe and stable beam deceleration and power extraction üHigh power two beam acceleration scheme recombination x 2 bunch length control fully loaded acceleration phase-coding structures 30 GHz recombination x 4 bunch compression PETS on-off structures two-beam acceleration 12 GHz deceleration stability Structures Structure materials Drive Beam generation PETS on-off DB decelerator CLIC sub-unit

CTF 3 status in the years 2004 Thermionic gun 2005 Linac DL F D F D F F D F D D FD F D D F CR 2006/7/8 D F D CLEX CTF 2 Photo injector / laser tests from Oct. 2008 30 GHz production (PETS line) and test stand CLEX 2007 -2009 building in 2006/7 Complete apart from TBL TL 2 2008 TL 2, TL 2’ installed

Main points of the commissioning ü Delay loop: § ü Ø 2 x current multiplication by DL TL 1: § 3. 5 A in TL 1 § Magnetic and RF injection in CR CR: § Bad cabling quadrupoles § Wrong BPM calibration § Combined function magnets not properly modeled § FAST VERTICAL INSTABILITY

The 2008 of CTF 3 30 GHz 30 GHz only DL & CR RUN 1 DL, CR, TL 2 TBTS Linac only Installation: TL 2, CALIFES, TBTS Today RUN 2 Linac, Ring area, (CLEX) PETS in TBTS Installations CALIFES PETS RUN 3

2008 CTF 3 experimental program • 1 st run (April - June) • Injector & Linac: establish stable & documented working point, automatic beam steering & steering algorithm studies, diagnostics consolidation, stability studies, EUROTe. V BPMs • Delay Loop: complete beam optics measurements (dispersion, orbit, kick measurements, matching), re-establish combination • TL 1 & combiner ring: complete optics studies (dispersion, closed orbit correction, matching, tunes, kick measurements, quad displacement evaluation, matching), tune and b function dependence of vertical instability, factor four combination with DL bypass (≥ 10 A) • DL, TL 1 & CR: factor 8 combination (≥ 15 A) • 2 nd run (July - September) • Complete DL + CR, new RF deflectors (20 A ? ) • TL 2 commissioning • First CALIFES commissioning • TBTS commissioning (no PETS) • 3 rd run (September - December) • Complete above program • Coherent Diffraction Radiation tests • TBTS, PETS running in

2008 CTF 3 experimental program • 1 st run (April - June) • Injector & Linac: establish stable & documented working point, automatic beam steering & steering algorithm studies, diagnostics consolidation, stability studies, EUROTe. V BPMs • Delay Loop: complete beam optics measurements (dispersion, orbit, kick measurements, matching), re-establish combination • TL 1 & combiner ring: complete optics studies (dispersion, closed orbit correction, matching, tunes, kick measurements, quad displacement evaluation), tune and b function dependence of vertical instability, factor four combination with DL bypass (≥ 10 A) • DL, TL 1 & CR: factor 8 combination (≥ 15 A) • 2 nd run (July - September) • New RF deflectors, Complete DL + CR (20 A ? ) • TL 2 commissioning • First CALIFES commissioning • TBTS commissioning (no PETS) • 3 rd run (September October - December) • Complete above program First CALIFES commissioning • Coherent Diffraction Radiation tests • TBTS, PETS running in

Measurements in CTF 3 Several measurements are performed in the machine to validate the optics models: § Response matrix: • • High precision method Symmetric and multiturn kick (ring) § Dispersion measurements § Tune measurements Steering algorithms applied in the machine: § Ring orbit correction § Dispersion free steering (Linac) Bunch length measurement Transient compensation

Gun instability Unstable Stable CTF 3 Linac is fully loaded The energy transferred to the beam depends on the beam current Gun instability o The current is different shot to shot o The energy gain is different shot to shot o Position jitter in dispersive regions o Set up and measurements VERY difficult (HV fluctuations) Problem solved since September 2008

Combiner ring CTF 3 commissioning status 13

Combiner ring kick measurements →To maximize the precision of the measurement in the ring: → The multiturn response matrix has been measured: easier to identify the discrepancies → Symmetric kicks analysis: easier to identify a single quad error → Several bugs found TURN 1 TURN 2 TURN 3

Combiner ring: correcting the bugs Dispersion →Combined function magnets (reused from EPA): →New model of the combined magnets has been used → The k 1 strength has been lowered with respect to the one used in the EPA model → Increase of the strength of the J-type quads → Cross-cabled control units for quadrupoles power converter Tunes

Tune measurements W/O correction Wiggler currents adjusted according to kick measurements W correction

Fast vertical instability disappeared! current vertical horizontal Old deflectors New deflectors BPM signals shoving vertical instability BPM signals, no instability

Transfer line TL 2 large part done by RRCAT: Optics design Aluminium vacuum chambers Bending magnets CTF 3 commissioning status 18

TL 2 optics Module-3 Module-2 Module-1 §Tunable R 56 (from -0. 35 to +0. 35) §Achromatic arc §Final matching doublet §Straight section for tail clipper § CLEX-CR buildings not at the same height (achromat) §Matching section §From CR extraction point to the first bend magnet (achromat) Beam direction For more details see “Optics design”, Amalendu Sharma et al. , 2007 CTF 3 collaboration meeting, Link

Beam setup in TL 2 MTV LINAC TL 1 CT DL CTS CLEX CR TL 2 → Quad scan in CTS and tracking to the start of TL 2 → Uncertainty on the initial conditions: → Error in the TL 1/CR model → Small variations of the quads strength in the TL 1/CR model → Error in the measurement propagated through TL 1 and CR → New equipment to read the BP in the line: → Some problems at the beginning of the commissioning → Relatively strong optics → Since a certain time radiation alarm made operation in this area slow and annoying

Beam through TL 2 → Uncertainty on the initial conditions: → Modified module-2 quads to compensate the possible different initial conditions → Found and corrected model-measurements discrepancies in CR (only during this shut down) → Installed MTV at the beginning of TL 2 (during this shut down) → Greatly improved the BPs reading (interactions with LAPP people) → Relaxed optics searched → Discovered bug: → last quadrupole of the first triplet of module-2 had a maximum value lower than the read one (Loic) TL 2 status at the end of the year BUT …

Kick measurements Kick 615 Kick 435 Kick 125 → Up to now NO huge discrepancies between the machine and the model found

For 2009 run improvements The operation of the machine was very tedious in the CR extraction zone because of radiation problems. CRM DL TL 1 CR CLEX TL 2 ü During this shut-down the two exit chicanes were extended Tail Clipper installed in TL 2: Ø It is made of kicker and dump that sits just above the beam Ø It allows to regulate recombined train length Ø The dump serves as a beam stopper to protect CLEX so It makes possible simultaneous operation of DL/CR and installations in CLEX

CLEX (CLIC Experimental area) existing building F DFD DFD F D F D FD DF D F D F F FD F D D D F DF DF Test Beam Line TBL 6 m DUMP TBTS 16 m DUMP D F F D FD DFD 16. 5 m 2. 5 m TBTS 2. 0 m F D D F D MP D F F D FD LIL-ACS F DU D 1. 85 m 8 m DFD F DFD 0. 75 DUMP DFD F D D F LIL-ACS DF P DUM LIL-ACS DF TL 2’ 2 m 22 m CALIFES Probe beam injector CALIFES Probe beam ITB (not base-line) 42. 5 m Two Beam Test Stand Probe Beam Everything installed, apart from TBL CTF 3 commissioning status 24

PETS A fundamental element of the CLIC concept is two-beam acceleration, where RF power is extracted from a high-current and low-energy beam in order to accelerate the lowcurrent main beam to high energy.

Drive beam generation scenarios CTF 3 #1 DL DBA CTF 2 CLEX TBTS CR <30 A CTF 3 #2 Operation mode DL 14 A CR #1 #2 #3 CLIC Current, A < 30 14 4 101 Pulse length, ns 140 <240 <1200 240 12 12 3 12 <280 61 5 135 Bunch Frequency, GHz CTF 2 CLEX PETS power (12 GHz), MW TBTS CTF 3 #3 DL 4 A CTF 2 CLEX TBTS CR To produce the CLIC nominal PETS power 22 A drive beam would be necessary.

The recirculation To the Load Variable phase shifter Variable Splitter (coupling: 0 1) PETS with external re-circulation PETS output Drive beam PETS input A fraction of the power going out from PETS is resent to the SAME PETS structure CLIC nominal 6. 0 A 5. 0 A 4. 0 A 3. 5 A 240 ns CLIC nominal R. Corsini, I. Syratchev Problem 2008 run: Splitter: stuck in undefined position (not remotely controllable) Phase-shifter: stuck in undefined position (not remotely controllable)

Beam in TBTS PETS story Total ~ 30 hours integrated conditioning time (15/11/2008 to 15/12/2008) Gradually increasing current arriving at PETS, up to ~ 5 A, 11/12 14/11: First beam 2 A w/ recirculation (by chance: positive build-up!) 21/11: Manually forces splitter to extreme position: no recirculation (to verify beam generated RF power) 28/11 : Adjusted phaseshifter : back to constructive recirculation mode

The recirculation: measurements With the maximum current sent to PETS (~5 A) this year 30 MW power obtained instead of less than 5 MW! Power: PETS out, to load, reflected Corresponding pulse intensity^2 (the BPM before, and two first after PETS): E. Adli, R. Corsini, I. Syratchev

The recirculation: model/measurements Model (power) Measured (current) E. Adli Very nice according of the modeling with the measurements

CALIFES commissioning DUMP TBL DFD D F DFD TBTS DFD MP DU D 1. 8 5 m F DUMP FDF F D F FD DF D D FD LIL-ACS F D F F D DF LIL-ACS – Earlier the laser was used by PHIN • The beam with laser pulse train of 100 ns length (150 bunches) • Dec 8 th – Laser broken – Measurements continued using the dark current • 30 th March – Restart LIL-ACS CALIFES Probe beam injector • Dec 1 st • 100% transmission through the 1 st cavity P TL 2’ DUM D DF

Steering algorithms Several steering algorithms have bee applied in the machine → Closed orbit correction (ring) → Dispersion free steering (Linac)

CR orbit correction algorithm Best eps value iteratively determined: → Tolerance on the maximum allowed beam displacement and maximum value of the currents in the correctors for i = 1: n_max_step if i == 1 eps(i) = eps_start*fact; else eps(i) = eps(i-1)*fact; end e value [theta_s, thetap_s, corr_s, final_s, idec_s] = correction_1_mod(eps(i), RM', x_BP'); Curr_tot_s(i, : ) = start_corr'+theta_s; Curr_tot_max(i) = max(abs(start_corr'+theta_s)); if abs(Curr_tot_max(i)) > max_I_corrs_tol fact = 1. 1; else x_max_exp = max(abs(x_BP+RM'*theta_s)); if x_max_exp < tol break else end fact = 0. 9; end Curr_tot = Curr_tot_s(end, : ); Check and new e value

CR response matrix Orbit closure: → The response matrix is built using both the first and the second turn orbits Kick at corrector 242 Turn 1 Turn 2 Correctors BPM/BPI Kicks in the correctors to measure the response matrix: → The value of the kick in each corrector is determined according to the maximum tolerated losses in the last read BPM/BPI

CR orbit correction: the results Inputs: → Tolerated maximum x-displacement = 4 mm → Maximum current in the correctors = 10 A → Maximum allowed losses = 10% Tolerance on the orbit correction limited by the incoming orbit jittering

Steering algorithms in the Linac E. Adli → The CTF 3 linac has been used as a facility of the TBL to test the Beam Based Alignment algorithm → Use this technique to steer the beam during the CTF 3 linac operation Structure of the CTF 3 linac (not to scale) → Studied algorithms: → All-to-all (A 2 A): steers the beam to get BPM zero-readings, by inverting the response matrix of the nominal machine optics → Dispersion free steering (DFS): minimizes (at the same time) of the orbit and the dispersion, using the responses corresponding to different optics: → Used responses: → Measured. Necessary to re-measure it each time the optics changes → Model-based. Nice model identification (BPM readings corrector strengths) necessary before

Steering algorithms in the Linac: the results E. Adli Linac orbit after all-to-all correction A 2 A worked well A 2 A (measured response) → convergence after 2 iterations A 2 A (model response) → convergence after 4 iterations Comparison between results of Dispersion Free Steering and All-to-All DFS worked well Simulated BPM offset: A 2 A → residual dispersion ~ 15 mm DFS → residual dispersion of a factor 3 smaller

Bunch length measurements H. Shaker, A. Dabrowski et al. Standard RF deflector and novel RF pickup technique M. Micheler et al. Use the radiation emitted by electrons passing close to a medium

Transient compensation A. Dabrowski et al. • 32 Tungsten plates (2 mm thick) spaced by ~1 mm • Energy along the pulse measurement Nominal RF settings Steady State Electrons ΔP/P (%) High Energy Transient ~ 40 % > E 0 Time (ns) Adjusted RF arrival timing Steady State ΔP/P (%) Transient compensation ~10% < E 0

Where is the drive beam? Phase coding recombination in DL 1. 5 GHz DL CR F D F D F F D F D D FD F D F D CLEX CTF 2 Beam all the way through CLEX Factor 4 recombination in CR

Where is the probe beam? Responsibility of IRFU (DAPNIA), CEA, Saclay Dark current K 10 20 25 beam dump 25 quadrupoles 15 MV/m 17 MV/m compression acceleration CALIFES

The 2009 of CTF 3 Sections in operation Linac PHIN CALIFES DL & Ring PHIN 30 GHz TL 2, TBL, TBTS (DB) CALIFES CLEX stop Delay Loop CALIFES TL 2 C. Ring TBTS TBL

DRIVE BEAM MODEL VALIDATION ü Gun instability disappeared ü Linac commissioned ü Delay loop factor 2 multiplication obtained ü Vertical instability in the combiner ring eliminated: factor 4 multiplication achieved ü TL 2 commissioning started ü Beam in PETS: power produced w and w/o recombination IN PARALLEL ü Steering algorithms (Linac and ring) üBunch length measurements üTransient compensation üFirst probe beam produced: CALIFES commissioning started PROB E BEA M ü Ultimate the commissioning of the new lines (TL 2+CLEX lines) üPut in operation DL and CR together to send ~30 A in PETS üFirst acceleration of the probe beam CTF 3 commissioning status 43

Extra slides

Delay loop principle double repetition frequency and current parts of bunch train delayed in loop RF deflector combines the bunches

RF injection in CR combination factors up to 5 reachable in a ring 1 st turn injection line 2 nd septum 1 st deflector Cring = (n + ¼) l 2 nd deflector local inner orbits RF deflector field 3 rd lo 4 rd lo/4

DL 2 Factor 2 in the delay loop achieved 1 3

Wiggler currents correction W/O correction W correction CTF 3 commissioning status 48

Tune measurements: the procedure → The measurement (oscilloscope + ”eyes”): f MAIN → Fractional part of the tune determined from the Fourier transform of the H (V) signal in a BPM: I f QL f QR H V → The sign is determined by the slope of the tune as a function of the quad strength variation → Compromise between oscillation amplitude and number of turns ü Nice reliability of the measurements Time consuming (H and V measurements can take also half a day) → The model comparison (automatic): → Scan of the tunes as a function of the current in a quads family → Scan over the energy range 49

Error in the CR model → For the several corrections of the TL 1/CR model the TL 2 behavior predicted by the model (TL 2 nominal optics) 50

“Small” distributed errors (TL 1+CR) → Random errors (gaussian mean = 0, s = 1% x INOM) in TL 1 and half of CR 51

But in any case … 52

CTF 3 commissioning status 53

The 2009 goals of CTF 3 30 GHz: Two structure test (TM 02) + breakdown studies CALIFES Beam characterization, beam to TBTS (most likely still reduced current) Delay Loop Back in operation, retrieve combination x 2 (~ 7 A) Combiner Ring Final optics checks, isochronicity, put together with DL (> 24 A) TL 2 Complete commissioning, bunch length control, > 20 A transported to users TBTS PETS to nominal power/pulse length (15 A, recirculation) Beam commissioning of probe beam line First accelerating structure tests (one structure ? – CLIC G) Two-beam studies (deceleration/acceleration), initial breakdown kicks studies TBL PETS validation (100 MW, need > 20 A), beam line studies (2 -3 PETS ? ) PHIN Beam characterization, reach ½ of nominal bunch charge ? Others CDR studies in CRM, beam dynamics benchmarking, stability studies, control of beam losses…

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