Results on recent technology developments at ATF - Beam extraction study by a Fast Kicker - N. Terunuma, KEK LER11, Heraklion, Crete, Greece, 2011/Oct/5

Beam Position Monitors 2/27

DR BPM Upgrade for 2 pm emittance The original read-out system designed for the single path position measurement has a 10  m resolution. Upgraded BPM readout system: FNAL Utilize analog down-conversion and digital signal processing techniques automatic gain-correction New functions for optics analysis Broadband turn-by-turn mode (< 10 µm resolution) Injection 1,000 turns Extraction 64 turns Narrowband mode with high resolution (~ 100 nm range) 160 ms, 500,000 turns after injection Further investigation for the system completion is continued. LO & CAN-bus Distribution New Timing Module & Custom Digitizers New Downmix & Calibration 3/27

ATF2 Cavity BPM system IP BPM system (BPM + Ref) Cavity 1 unit Target : 2 nm Aperture: 6 mm(V) S-band BPM system BPM cavity: 4 units Ref. cavity: 1 unit Target : 100 nm Aperture:  40 mm C-band BPM system BPM cavity: 34 units Reference cavity: 4 units Target resolution: 100 nm Aperture:  20 mm KNU / PAL / KEK / RHUL / SLAC 4/27

Present Status of the ATF2 Cavity BPMs S-band BPM Resolution ~ 1  m Jitter subtracted calibrations Cavity frequency correction Amplifiers were not sufficient. IP-BPMs Just installed to assist the small beam size study. Not yet well calibrated! Further investigations are continued. BPM number C-band BPM 20 dB attenuation, most of C-band BPMs to widen the dynamic range Resolutions: with 20dB att. ~ 200 nm w/o 20dB att. ~ 50 nm (well centered beam w/o saturation  27 nm) By S. Boogert (RHUL) 5/27

Fast Kicker R&D at ATF The fast kicker R&D has been one of the missions at ATF for the ILC technology development. The bunch separation in the ILC damping ring is 6 ns for a nominal operation (RDR, SB2009), 3 ns for a possible luminosity upgrade. ILC fast kicker: should meet these requirements, 0.6 mrad ~20 units 1.5 MHz, +-10 kV, Stability <0.1%, Multi-units of strip-line kicker +10kV -10kV 6/27

Fast Kicker R&D at ATF 7 Pulser performance study (2005~2009) It has been done here by measuring the beam oscillation. Demonstration of a Beam Extraction (2009~) Swap the conventional pulse kicker with the fast kicker but only in this R&D period

Requirement for ATF beam extraction The fast kicker R&D for a beam extraction had been performed by exchanging the conventional pulse magnet. It was done only when the study was scheduled because its reliability for other R&Ds was not known well. The beam extraction system of ATF DR has to have a beam kick angle of 5 mrad. It is difficult to realize by a fast kicker itself under the limited space obtained by replacing the conventional pulse magnet. Therefore, we needed followings. pulsed orbit bump in DR as much as possible when a beam is extracted, aux. septum magnet before the present one, finally, optimize a gap between two electrodes but as large as possible. 8/27

2015/12/69 Beam Extraction Orbit using Strip-line Kicker, Aux. septum & Pulse bump To existing septum magnets Bump orbit Stored beam Local Bump Extracted beam 9/27

(FID Co. Ltd) 10/27

Kicker pulse (10kV) Kicker field Rise time 1.5 ns Rise time 5 ns 11/27

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Fine delay control window of the kicker pulse Trigger system for fast kicker Beam extraction signal

Single-bunch beam extraction by a fast kicker 14

15 1 st Beam Extraction from DR to ATF Oct. 22. Beam profile at MS1X screen monitor, which is located at the downstream of the septum magnets. 15/27

16 Jitter 1.05e-6/3e-3=3.5e-4Jitter 2.24e-6/3e-3=7.4e-4 Kick angle jitter of a fast kicker for single bunch Fast Kicker ATF2 Cavity BPMs Angle (urad) 2010/Oct 2010/Mar Stability of the fast kicker was evaluated by using R12 and beam positions measured with the 100 nm-resolution BPMs. 16/27

Multi-bunch beam extraction by a fast kicker 17

2015/12/618 Multi-bunch beam extraction by the Fast kicker in DR: 3 Trains, 9(max 10) bunches/train with 5.6 nsec spacing Extracted: 27(max 30) bunches with 308 ns spacing bunch-by-bunch profile follows that in the DR. bunches were extracted from the last bunch to the first bunch. 3 trains in DR Intensity of extracted bunches 18/27

MB-Orbit and jitter measurement Pulses Kick Angle variation for pulsesStability of each pulses The jitter ratio for the kick angle was distributed from 1x10 -3 to 4x10 -3 for each pulse. This value is larger than the single bunch jitter. 19/27

Profile of the kick field and the jitter Plot shows the beam position at MQM16FF BPM, when scanned the kicker pulse timing. There is no flattop of the kick field. The jitter increased at the both side of the peak. To make stable beam kick, careful timing adjustment of four pulses is needed. 200ps Trigger Timing (ns) Kick field scan BPM x-position (um) 20/27

1 st results of multi-bunch extraction, 2010/06/17 The intensity of each bunch was not flat and unstable. The x-position of extracted beam was clustered as bi-stable. Extracted beam position (x) Extracted beam intensity HV pulse arrival Pulse number Relative (ns) Very much complicated. Different behavior on each pulser! 21/27

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Timing adjustment circuit was installed w/o delay with delay Use for beam extraction Not perfect but much better Pulse-train delay adjustment circuit; common trigger for each pulser is adjusted pulse-by-pulse. No inter-pulser adjustment. Pulse number Relative (ns) 23/27

2 nd results of multi-bunch extraction, 2010/10/26 Stable beam extraction was confirmed at the extraction line. The beam reach to the beam dump without any beam loss. 30 bunches of the beam are stored to the DR, stably. 24/27

Photos were taken just a day before earthquake! INFN stripline for the study at ATF Collaboration of KEK and INFN Low impedance stripline based on the design for DA  NE It was delivered to ATF in March We will install it in DR for the evaluation of impedance, but not for a beam extraction. 25/27

The stored current decreased gradually when the total current becomes higher. It was recovered after several minutes. We suspect the physical deformation of the strip-line electrode due to the heating by wake or SR. Challenging “small gap to enable the extraction at ATF” may leads this difficulty. This may be an issue “only at ATF”. Difficulty under the higher current “at ATF” single bunch 1 train 9 bunch 1 train Itot=2x bunch 3 train Itot=6x10 10 Blue: Stored current in DR 2hour 26/27

Conclusion The beam extraction by a fast kicker system has been successfully demonstrated at ATF. Further studies on the improvement of the pulser performance and its reliability for long term operation should be continued, but it will not request a beam. Honestly, we have a difficulty on the fast kicker operation under higher intensity beam. It is due to the design under the limited space for extraction in ATF. Further, we will proceed a beam test of the low impedance stripline designed and delivered by INFN, Italy in a near future. 27/27

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