1. Managed by UT-Battelle for the Department of Energy SNS BLM System Overview Detectors, Measurements, Simulations Alexander Zhukov Saeed Assadi SNS/ORNL

2. 2Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 Liquid Hg Target SNS Accelerator Complex Front-End: Produce a 1-msec long, chopped, H- beam 1 GeV LINAC Accumulator Ring: Compress 1 msec long pulse to 700 nsec Ion Source 2.5 MeV 1000 MeV 87 MeV CCL SRF,  = 0.61 SRF,  =0.81 186 MeV387 MeV DTL RFQ RTBT HEBT Injection Extraction RF

3. 3Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 BLMs at SNS  Major MPS device –Fast MPS – abort the current beam pulse within 10 μS (hardware – analog integrator), not applicable to RTBT –Slow MPS – keep average loss reasonable  Diagnostic device - machine tuning  Activation “planning”  Activation decaying  Activation buildup ?  Halo measurement with the help of WS Detectors used –Ion chambers ~300+ –Neutron detectors ~30+ –Low level neutron detector 8 –PMTs ~10+

4. 4Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 Ion Chambers  Argon filled, 113 cc volume, 2 kV bias.  Response 70 nC/Rad  Slow ~1 μS (charge collection)

5. 5Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 Neutron Detector  35 mm poly moderator  Li (n,alpha)  Scintillator  PMT  10 4 – 10 8 n/cm 2 /s  0.03eV - 3MeV

6. 6Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 Low Level Neutron Detector  85 mm poly moderator  B (n,alpha)  Counter  10 2 – 10 4 n/cm 2 /s  0.03eV-10 MeV

7. 7Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 PMT  Scintillator  PMT  Response 50 pC/MeV  Fast ~10 nS

8. 8Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 ND IC 1 mS Neutron Detector vs. Ion Chamber  Commons –Analog output –Same electronics, low level software, MPS interface  Differences –Distance range: IC – local, ND remote –HV controlled dynamic range for NDs –Neutron signal originates from beam loss only, in contrast there are several x-ray sources –Waveform shape (neutron moderation in NDs) Proton Energy, MeV

9. 9Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 Challenges: Low energy part of linac  low energy beam (<20MeV) –IC not sensitive enough –ND sensitive, but hard to calibrate (no sufficient experimental data for reliable simulation) –Still the biggest issue –PMTs are supposed to help Warm linac PMTs

10. 10Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 Challenges: WF subtraction –Cavity X-rays give significant input to loss signal –The software subtracts the RF only waveform (the beam rep rate is 59.9 Hz to allow one reference signal per 10 seconds) –Fast MPS is compromised 1 mS X-ray Beam loss

11. 11Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 Noise BLM PMT HV OFF PMT BLM Loss HV ON Challenges: RTBT noise RTBT noise/EM interference with the beam or image current Problem is present with beam only Gets worse with beam charge increase

12. 12Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 Challenges: RTBT noise (continued) Low Level NDs Counter output (solves noise issue) Registration of time distribution effectively increases dynamic range Capable of registering losses from 1 mini-pulse Need time to collect statistics 10 s ~ 600 pulses 1 mini -pulse 150 mini -pulses saturation 10 mS

13. 13Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 WS and halo studies Loss / WS conversion constant Attempt to improve WS performance in halo part Special scintillating fiber Ordinary IC Scan of loss signal vs WS position gives good measurement around the beam center, but halo shape isn’t really detectable Optimized fiber is being designed

14. 14Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 shutdown begins Activation decaying NDs in SCL HV ramped up Using gamma sensitivity

15. 15Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008  Standard IC & ND amplifier –High channel density –Obsolete parts (big problem!) –3 gains jumper settable  VME ADC –24 bits for dynamic range (~10 bits digitizing noise) –High channel density –100 kS sampling rate  VxWorks based EPICS running WF subtraction at 60 Hz  PMT custom made amplifier/HV boards + cRIO + LabVIEW RT  Low Level ND LabVIEW on Windows Electronics and Low Level Software Currently running production system

16. 16Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 Electronics and Low Level Software Future  FPGA based WF subtraction –Test with cRIO based PMTs currently installed –Increase of sampling rate is desirable  Choosing FPGA platform –VxWorks vs. PXI vs. cRIO ?  Smart devices for higher beam availability –Every detector has its own hot pluggable data acquisition board –Complete replacement of 1 channel should not affect other channels (no beam downtime) –Full remote configuration: all setup data come from one source (Oracle)

17. 17Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 High Level Software Lossviewer2 (XAL application) BLM statistics web site

18. 18Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 Simulations (MC transport codes)  High Energy  Hadrons (primary protons, cascade hadrons) MCNPX, SHIELD, G4, MARS  Low Energy Neutrons MCNPX, G4  Electromagnetic Showers MARS,  EGS4, G4  Low Energy electromagnetic interactions  EGS4, G4  Beam PARMILA  Low Energy Protons MCNPX  MARS, SHIELD, G4  RF, dark current  ??? Ultimate goal Recreate the loss location and absolute value using BLM measurements Proton Energy, MeV

19. 19Managed by UT-Battelle for the Department of Energy A. Zhukov SNS BLM System Overview Detectors, Measurements, Simulations WGF04 - HB2008 8/26/2008 Thank you!