1. Demonstration of the Beam loading compensation (Preparation status for ILC beam loading compensation experiments at ATF injector in this September) (PoP experiment on beam loading for truly conventional positron source at ATF injector ) AWLC14 at FNAL, 12-16 May 2014 KEK, Junji Urakawa Contents : 1. Short review of conventional positron source for ILC 2. 300Hz Linac Scheme for Beam Loading Compensation using TW. 3. Plan for beam loading compensation experiment at ATF 4. Preparation status 5. Summary

2. 1. Short review of conventional positron source for ILC A conventional positron source for international linear collider, NIM A Volume 672, 21 April 2012, Pages 52-56

3. Time structure of beam 0<t<264.45ns, i=0.532A 264.45<t<362.85ns, 0A 362.85ns<t<627.3ns, 0.532A 627.3ns<t<725.7ns, 0A 725.7ns<t<990.15ns, 0.532A 0.532A is beam loading current.

4. Bunch by bunch extraction from Damping Ring to make ILC beam train. This is the model for positron target system to confirm the generation of ILC positron beam.

5. Phase to Amplitude Modulation Method for Beam Loading Compensation 300Hz Power Supply Low Level RF Phase Shifter and Amp. 3dB High Power RF Combiner 50  High Power Terminator 80MW Klystron 2. 300Hz Linac Scheme for Beam Loading Compensation

6. 300Hz Power Supply Low Level RF Phase Shifter and Amp. 3dB High Power RF Combiner 50  High Power Terminator 80MW Klystron 3m long constant gradient travelling wave structure We need the precise control of the phase shifters. Also, I assume 10% margin as wave guide loss and so on because of the experience at ATF Linac. So, klystron output power 80MW and 3  s pulse width are necessary. 3x10 10 positron/bunch 300Hz triplet beam Less than +/- 0.7% Beam loading current 0.78A.

7. Detail of beam loading compensation: Less than ±0.7% is possible For ILC 300Hz multi-bunch beam. Control of input RF power by phase shifters

8. 12.5Hz Power Supply Low Level RF Phase Shifter and Amp. 3dB High Power RF Combiner 50  High Power Terminator 80MW Klystron 3m long constant gradient travelling wave structure Essential Beam Loading Compensation Scheme for proof-principle experiment at ATF in this September 300ns 53.2ns

9. ATF laser system for photo-cathode RF Gun can generate triplet laser beam of 20 pulse with 2.8ns bunch spacing and about 100ns gap by minor modifications. 357MHz Laser oscillator Pockels cell to make triplet laser pulse train 12.5Hz Amp. 4 th higher harmonics generator (crystal:BBO)

10. Photo-cathode RF gun (electron source) S-band Linac Extraction line Damping Ring 3. Plan for beam loading compensation experiment at ATF

11. 12.5Hz Power Supply Low Level RF Phase Shifter and Amp. 3dB High Power RF Combiner 50  High Power Terminator 80MW Klystron 3m long constant gradient travelling wave structure We need the precise control of the low level phase shifters. Also, I assume 10% margin as wave guide loss and so on because of the experience at ATF Linac. So, klystron output power 80MW and 3  s pulse width are necessary. 1.4x10 10 electrons/bunch with 2.8nsec bunch spacing and 2856MHz Linac beam loading current: 0.78A

12. 3.6 cell RF Gun 3m long TW 3x10 10 with 6.15nsec bunch spacing corresponds to 1.4x10 10 in the case of 2.8nsec bunch spacing with same beam loading in multi-bunch trains. ATF Triplet Beam : 3x20 bunches/train with 60nsec train gap and 2.8nsec bunch spacing. This operation is possible in the safety of the radiation for ATF accelerator. However, since I want to make more safety margin, following doublet beam scheme is proposed. 45 degrees bending magnet to measure the energy of multi-bunch Beam Transport ATF Injector for 1.3 GeV ATF Linac will be modified for beam loading compensation experiment in this summer.

13. 80MW, 4.5  s 12.5Hz Power Supply Low Level RF Phase Shifter and Amp. 3dB High Power RF Combiner 50  High Power Terminator 80MW Klystron 3m long constant gradient travelling wave structure Essential Beam Loading Compensation Scheme for proof-of-principle experiment at ATF 166.4ns 53.2ns ~60.0ns

14. 3.6 cell RF Gun SW 3m long TW 45 degrees bending magnet to measure the energy of multi-bunch 12.5Hz Power Supply Low Level RF Phase Shifter and Amp. 3dB High Power RF Combiner 50  High Power Terminator 60MW Klystron fast phase control Energy spread 0.1% in rms 150 bunches/pulse with 2.8ns bunch spacing Generation of three mini-train per pulse 12.5Hz Power Supply 2nC/bunch Chicane Amplitude Modulation 40MW, 1.5  s 80MW, 3  s

15. ATF laser system for photo-cathode RF Gun can generate doublet laser beam of 20 pulse with 2.8ns bunch spacing and about 100ns gap by two Pockels cells. 357MHz Laser oscillator Pockels cell to make doublet laser pulse train 12.5Hz Amp. 4 th higher harmonics generator (crystal:BBO) Delay line

16. Present laser system, Two Pockels cells, 1.6 cell RF Gun, Chicane and BPM were used to generate doublet pulse train and to measure energy of each bunch. 0.78 x10 10 electrons per bunch.

17. Waveguide system should be changed to match the beam loading experiment after summer shutdown of ATF operation. Following plan was proposed and necessary components were ordered. We want to start the change of the waveguide system from mid. of July and will complete it by mid. of August. Present waveguide for KLY#0 Present waveguide for KLY#1 Present waveguide for KLY#2

18. KLY#0 KLY#1KLY#2 KLY#0 KLY#1 KLY#2 Present waveguide system New waveguide system for beam loading compensation experiment To Gun To L0 3.6 cell RF Gun SW L0 3m long TW 45 degrees bending magnet to measure the energy of multi-bunch Generation of two mini-train per pulse Chicane

19. Several modules and function generators were ordered for the control of RF phase and amplitude which are necessary for the beam loading compensation experiment. We will install necessary control devices and monitor system by mid. of August. Then, we will start the RF aging and test new instrumentation from end of August. Function Generator I-Q modulation & detection

20. 3.6 cell RF Gun 3m long TW 2x10 10 with 6.15nsec bunch spacing corresponds to 0.9x10 10 in the case of 2.8nsec bunch spacing with same beam loading in multi-bunch trains. 3x10 10 with 6.15nsec bunch spacing corresponds to 1.4x10 10 in the case of 2.8nsec bunch spacing with same beam loading in multi-bunch trains. 45 degrees bending magnet to measure the energy of multi-bunch Beam Transport Injector for 1.3GeV ATF Linac will be modified for beam loading compensation experiment in this summer. Due to the lack of 2013 budget, we delayed this experiment, sorry. 5. Summary

21. 3.6 cell RF Gun SW 3m long TW 45 degrees bending magnet to measure the energy of multi-bunch 80MW, 3  s 12.5Hz Power Supply Low Level RF Phase Shifter and Amp. 3dB High Power RF Combiner 50  High Power Terminator 60MW Klystron Energy spread 0.1% in rms 150 bunches/pulse with 2.8ns bunch spacing Generation of three mini-train per pulse 40MW, 1.5  s 12.5Hz Power Supply 1nC/bunch Chicane Amplitude modulation