SARAF commissioning & safety issues. L. Weissman on behalf of the SARAF team SPIRAL week 2010

Transcription

1 SARAF commissioning & safety issues L. Weissman on behalf of the SARAF team SPIRAL week

2 Outline commissioning of SARAF project : RFQ status Cryomodule status Accumulated beam operation experience Safety topics : Experience with a few ma low-energy deuteron beam (outsourced to the poster) Neuron shielding by thick concrete Criterion for hands on maintenance accelerator 2

3 SARAF Layout RF Superconducting Linear Accelerator Target Hall Phase I Phase II Designed and built by RI (former ACCEL); being commissioned by RI and local stuff A. Nagler et al., LINAC

4 SARAF Phase I Upstream View PSM MEBT RFQ LEBT EIS A. Nagler, Linac-2006 C. Piel, EPAC-2008 A. Nagler, Linac-2008 I. Mardor, PAC

5 SARAF Phase I Downstream View PSM Beam Dump 2 Beam Dump 1 D-Plate 5

6 176 MHz 4-Rod RFQ (built by NTG) RFQ Beam Properties Beam Parameter Protons Deuterons Energy (MeV) 1.5 (1.5) 3.0 (3.0) Maximal current [ma] Transverse emittance, r.m.s., normalized, 100% [π mm mrad] 0.5 ma, closed LEBT aperture) 4.0 (CW) (4.0) 2.5 (10-4 ) (4.0) 0.17 (0.30) NM (@ 4.0 ma, open LEBT aperture) Longitudinal emittance, r.m.s., [π kev deg/u] (@ 3.0 ma) Transmission [%] (@ 0.5 ma) (@ 2.0 ma) (@ 4.0 ma) 0.25 / 0.29 (0.30) 30 (120) 80 (90) 70 (90) 65 (90) NM NM NM NM 70 (90) RF Conditioning Status Input Power [kw] Duration [hrs] 190 (CW) (CW) (CW) (DC = 80%) 0.5 Deuteron operation requires conditioning up to 260 kw CW (65 kv) I. Mardor et al, SRF workshop

7 Example of recent conditioning campaign Forward RF Power (kw) Goal Duty Cycle (%) The objective of the RFQ conditioning has not been achieved yet Pressure (10^-7 mbar) Goal Average power (kw) 7

8 Failures and solutions Discharge between rods and stems 8

9 Failures and solutions Heating of the end flanges 9

10 Failures and solutions Burning of tuning blocks 10

11 Failures and solutions Melting plunger. Failing RF contacts 11

12 Failures and solutions Failure of vacuum and water seals 12

13 Many RFQ components were redesigned and exchanged We hope that the process of RFQ debugging will converge after a few more iterations At present we can operate CW proton beam and deuterons at 20-30% duty cycle 13

14 Prototype SC Module (PSM) General Design: Houses MHz HWRs and 3 sc solenoids Accelerates protons and deuterons from 1.5 MeV/u Very compact design in longitudinal direction Cavity vacuum and insulation vacuum separated Beam 2500 mm M. Pekeler, LINAC

15 Before PSM commissioning Radiation (mr/h) 10 1 HWR1 HWR2 HWR3 HWR4 HWR5 HWR6 Helium processing ( mbar up to 43 MV/m pulsed) reduced field emission from the cavities and allowed stable operation at higher fields After Epeak (MV/m) 100 Radiation (mr/h) 10 1 HWR1 HWR2 HWR3 HWR4 HWR5 HWR6 0.1 A. Perry et al, SRF2009 workshop Epeak (MV/m) 15

16 PSM commissioning at SARAF Measurements of the piezoelectric tuner tuning range showed a reduction by a factor of 2. The Cryostat was opened and the piezoelectric actuators were exchanged. Analysis done by the manufacturer revealed a fault of electrical contact due to differential expansion. The tuning range of the new-piezos was measured and found to be higher. However, recent measurement indicate a reduction again. Change the resonance frequency by expanding or compressing the cavity 16

17 Issues under investigation 150 Cavity phase from AD Phase[Degrees] Time[Sec] Coupler temperature increase during RF operation in HWR4 Probably insufficient heat removal Cavity Trip Stable operation at moderate gradients (E P ~15MV/mV acc ~500kV) Frequent trips at higher gradients. 17

18 Beam operation (phasing) Example of cavity phasing Proton beam, low duty cycle (10-4 ) Scattering beam on thin gold foil Energy (MeV) HWR kv kv phase (deg) Energy (MeV) HWR phase (deg) Energy (MeV) HWR phase (deg) 200 kv 460 kv Energy (MeV) HWR 3 L. 1.8 Weissman 200 kv et al, DIPAC kv phase (deg) Energy (MeV) HWR6 200 kv phase (deg) 18

19 HWR4 Beam operation (phasing) Example of cavity phasing Deuteron beam, low duty cycle (10-4 ) Energy (M ev) kv 445 kv HWR 1 phase (deg) HWR Energy (M e V) Energy (M ev) phase (deg) HWR3 200kV 425kV phase (deg) Ene rgy (M e V) Energy (MeV) kv 410 kv phase (deg) HWR phase (deg) 300 kv 700 kv 19

20 Beam operation (CW proton beam) After phasing gradually increase duty cycle and beam current Long stability test : CW proton beam ma, at energy 3.15 MeV Kept for 8 hours Sharp jumps in vacuum each time as we open beam gate Further increase of current (up to 1.5 ma CW) lead to trip of cavities which was correlated with instability in cryogenics 20

21 Beam operation (transmission) Transmission (%) CW CW % CW % Input current/lebt FC (microa) 21

22 Beam operation (RFQ steering) Profile X Current (rel. un.) kw 66.5 kw 60.5 kw 57.8 kw 55.7 kw 52.8 kw Position (mm) Profile Y 10 Current (rel. un) kw 66.5 kw 60.5 kw 57.8 kw 55.7 kw 52.8 kw Position (mm) 22

23 Summary of the project status During the 2009 year the significant progress was achieved: a. first experience with proton/deuteron beam acceleration b. first experience with high duty cycle proton beam c. a number of serious RFQ modifications d. and, most importantly, accumulation of expertise by local stuff The International Steering Committee gave recommendation for going forward with the second phase of the project. Waiting for green light the Israeli Atomic Energy management. A lot of work still have to be done to bring the Phase I of the project to the required specifications a. conditioning of RFQ up to the fields needed for CW deuteron beam b. understanding of beam optics c. improvements control, infrastructure ectr. 23

24 Measurements of neutron fluxes from d(d,n) reaction with 40 kev 5 ma beam (details in the poster) 1,2 (CR-39 tags) 19,20 EIS 3,4 sol1 5,6 beam stopper dipole 7,8 21 aperture 9,10 1 m ~ 5 hours net time/5 ma in average and 2 m A on FC overnight sol2 22 concrete wall X-Y slits Seforad spectrometer X-Y wires scanners FC 11,12 13,14 15,16 Snoopy monitor 17,18 RGA Indium samples sol3 temporary beam blocker 24

25 CR-39 results 38 background EIS 315 sol1 138 beam stopper dipole 33 background aperture m sol2 background X-Y slits 340 concrete wall X-Y wires scanners FC sol3 624 temporary beam blocker 25

26 1.E+05 Q, thermal neutrons 1.E+04 Counts 1.E+03 3/4E n, E max 3 He E n, E max protons 2.45 MeV neutrons E n +Q 1.E+02 1.E Energy (kev) 26

27 Measurements of neutron fluxes (Seforad spectrometer) 3 He + n 3 H + p + Q(0.764 MeV) 27

28 Summary of the measurements (source of 2.45 MeV neutrons from the graphite FC ) Measurement Deuteron current (ma) # neutrons (n/s) # neutrons per ma (n/s/ma) Radiation tags 5 6.5(2.5) (5) 10 6 Snoopy monitor 5 9.0(20) (4) 10 6 Indium activation 2 5.1(10) (5) 10 6 Seforad spectrometer 5 1.1(2) (4) 10 6 Rule of thumb: fast n/s per 1 ma of 40 kev deutron beam on our FC In addition from activation measurements, 7.0(5) 10 3 thermal neutrons/s/ma L. Weissman et al. Health Physics

29 Concrete shielding of 14 MeV neutrons The d-t generator was placed at the SARAF accelerator building. CR-39 tags were distributed around. Operation time 32 min. Fast neutron yield was measured to be 1.73 x 10 9 n/s in 4π A 7,8 9,10 Earth North 4" dia cable ports ,18 19, A-A 137 cm 11 15,16 Linac beam corridor Service corridor BPE ,8 100 d-t generator 12 13,14 9, A 13, D. Berkovits et al, internal report 29

30 A Results A-A 165 background Earth North 4" dia cable ports 150 background cm d-t generator 463 background Linac beam corridor Service corridor BPE background 338 d-t generator background A 110 Sensitivity of CR-39 is 20 mrem Snoopy monitor placed in pos of tugs 7,8 showed 40 mrem/h Outside the building or on the second floor the Snoopy showed background 30

31 Results (continuation) A-A 4" dia cable ports Linac beam corridor Service corridor d-t generator 100 Additional tags were also placed in front of the opening between 50 cm thick blocks These tags yielded 221 mrem 31

32 Estimated dose rate along SARAF with losses of 1 na/m 30 cm from the beam pipe, 100 days of irradiation, 4 hours after shutdown 1.E+01 1.E+00 Dose rate (mrem/h) 1.E-01 1.E-02 1.E-03 Co-56 Co-55 Co-57 Mn-52 Mn-54 Mn-56 Total 1.E Position (m) S. Halfon et al, internal report 32

33 Beam loss criterion Allow losses for hands on maintenance (na/m) Calculated losses 10 mrem/h* 2 mrem/h* 1 W/m 1 na/m 50/20/5 na/m SPIRAL2 [4], IFMIF [6] IFMIF [5] Unconstrained "hands-on for SARAF [1,2] SARAF old Position along SARAF SC linac (m) * Beam loss criterion which will yield the specified dose rate along SARAF SC linac [1] J. Alonso, "Beam loss working group report", The 7th ICFA mini-workshop on high intensity high brightness hadron beams, Lake Como, Wisconsin, September [2] R. A. Hardekopf, "Beam loss and activation at LANSCE and SNS", The 7th ICFA mini-workshop on high intensity high brightness hadron beams, Lake Como,Wisconsin, September [4] T. Junquera et. al., Status of the construction of the SPIRAL2 accelerator at GANIL, Proc. Of LINAC08, Victoria, BC, Canada, [5] M. Sugimoto and H. Takeuchi, low activation material applicable to the IFMIF accelerator, Journal of Nuclear Material, (2004) [6] P. A. P. Nghiem et. al., Parameter design and beam dynamics simulations for the IFMIF-EVEDA accelerators, Proc. Of LINAC08, Victoria, BC, Canada,