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SNS Beam Loss Monitor System

SNS Beam Loss Monitor System. David M. Gassner Richard Witkover BNL. BLM System Requirements. Protect the machine from high activation due to slow, low-level losses (1W/m criteria) Protect the machine from radiation damage due to fast high-level losses (Beam Permit/Inhibit Link)

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SNS Beam Loss Monitor System

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  1. SNS Beam Loss Monitor System David M. Gassner Richard Witkover BNL SNS Beam Loss Monitor

  2. BLM System Requirements • Protect the machine from high activation due to slow, low-level losses (1W/m criteria) • Protect the machine from radiation damage due to fast high-level losses (Beam Permit/Inhibit Link) • Provide measurements of loss for tuning • Will not be used for personnel safety SNS Beam Loss Monitor

  3. Ion Chamber SNS Beam Loss Monitor

  4. Gain and Threshold adjustment • Gain Programmable • Beam intensities • Ring varies 103 during macro-pulse • RTBT can vary 103 between single turn, full intensity • Detector shielding • Loss limit thresholds programmable • Individual Channel levels • Separate levels for Fast and Slow losses • Trip outputs can be masked for studies SNS Beam Loss Monitor

  5. Ion Chamber Response Time SNS Beam Loss Monitor

  6. SNS Beam Loss Locations Locations of possible beam loss in the Ring Arcs. R. Hardekopf, LANSCE CCL Losses SNS Beam Loss Monitor

  7. BLM Distribution Total: 267 Ion Chambers in Linac, HEBT, Ring, & RTBT Linac DTL At tanks CCL At quads SRF On top of, and between doublets (4m apart) Transports At quads, collimators, dumps. Ring - 44 at quads (beta max) - Injection, extraction, collimators, RF - relocatable units SNS Beam Loss Monitor

  8. Linac Loss Monitors DTL 12 BLM’s, at each of the Tanks, Energy 2.5 to 86 MeV, length 36.5 m CCL 24 BLM’s, at every other Quad, Energy 86 to 186 MeV , length 55.4 m SRF 64 BLMs should be located above the doublets and midway between the doublets. This would space the BLMs at about 4 meters. Energy 186 to 949 MeV, length 235 m. SRF-64CCL-24DTL-12 SNS Beam Loss Monitor

  9. HEBT Loss Monitors 169 meters BLM LocationQuantity Quads 37 Collimator 2 Cavities 2 Dump 2 BIG 1 Moveable 8 FBLM LocationQuantity Upstream 1 Bend 1 Dump 1 SNS Beam Loss Monitor

  10. Ring Loss Monitors 248 meter circumference BLM LocationQuantity Quad 44 Injection 7 Collimators 7 RF 5 Extraction 5 Moveable 7 FBLM LocationQuantity Injection 2 Straight Sec. End 4 Bends 4 Extraction 2 SNS Beam Loss Monitor

  11. RTBT Loss Monitors 150 meters BLM LocationQuantity Quads 27 Collimators 4 Dump 2 Target 3 Moveable 4 FBLM LocationQuantity Extraction 1 Collimators 1 Target area 1 SNS Beam Loss Monitor

  12. SNS BLM Signal Routing Configuration Electronics located in service buildings. Linac Diagnostic Racks (available every 70 feet) DTL (12 channels) 1 Rack 1 Crate CCL (24 channels) 1 Rack 1 Crates SCL (64 channels) 1 Rack 2 Crates HEBT Service Building 52 channels 1 Rack 2 Crates RING Center Building 75 channels 1 Rack 3 Crates RTBT Service Building 40 channels 1 Rack 2 Crates Each location will have one or more front end computers through which BLM’s will communicate with the Permit Link and high level controls system. SNS Beam Loss Monitor

  13. EXPECTED LOSSES • HEBT, Ring and RTBT designed to have collimators as limiting apertures • Can we have any losses at other points? • Gas stripping • Linac RF (HEBT losses) • First turn injection mis-steering • Kicker misfire • HEBT, RTBT steering mis-setting ? • Beam-on radiation dose rates • TN-077 has provided answers for collimators • Other papers? SNS Beam Loss Monitor

  14. DOSE RATES LIMITS • Slow Loss: 1 W/m limit • Corresponds to ~10-4 distributed around 248 m Ring or 4 x 10-7 of total beam lost per meter • Gives 60-100 mrad/hr at 1 ft beam-off activation • “Rule of thumb”: Multiply by 1000 to get corresponding average dose rate during beam on • Need to resolve 2 decades below this to reasonably measure 1 W/m (4 x 10-9 of total beam/meter ) • What is maximum Fast (high-end) loss? • If we take 1% lost at a single point the total range is 2.5 x 106 , equivalent to 21-bits + sign • May want several bits higher to not saturate ADC • Low-end resolution limited by noise and BW, upper end by detector or electronics saturation (BLM expected to show effects at 5-10% loss SNS Beam Loss Monitor

  15. Ion Chamber Loss Detectors Ion Chambers - Glass bottle Evolution: Tevatron RHIC SNS 725 mm of Argon, 113 cc volume, 2 KV bias. Response 70 nC/Rad, about 20 pA/Rad/hr. Individual Calibrations, 95% within +/- 5%. SNS Beam Loss Monitor

  16. RHIC Ion Chamber BLM Detector SNS Beam Loss Monitor

  17. Ion Chamber Dynamic Range - High Fast Response for Beam Abort (electrons only) For 10us rise time, BW would be 35 kHz. (550 pA noise) This reduces resolution to 30 Rad/hr Intention is to observe large fast losses 104 – 106 Rad/hr Upper Limit Tests at LANL indicate similar BLMs start to saturate at a dose of 106R/sec This corresponds to about 5-10 % loss of full beam at one location SNS Beam Loss Monitor

  18. SNS BLM Analog/Digital Front End SNS Beam Loss Monitor

  19. VME Implementation SNS Beam Loss Monitor

  20. Liquid Cell/Photo-Multiplier Loss Monitor Features • Rise Time ~2nS • Installed at injection, extraction, ring bends & straight section ends. Detector • Available commercially from Bicron (MAB, using BC-505) • 1,2,4 Trimethybenzene, Hamamatsu 2060 PMT, 10 stage. Signals • Instabilities • Kicker errors • Momentum errors • Losses within bunch • Signals buffered and sent through wideband mux to fast digitizer (1 Gs/s). • Signal integrated over bunch duration, read out via fast digitizer clocked revolution frequency. SNS Beam Loss Monitor

  21. FBLM - Liquid Cell & Photo Multiplier SNS Beam Loss Monitor

  22. Data Acquisition IC BLM’s • Fast – 16 bits (incl sign), 200 kSa/s = 400 samples/macro pulse/blm. • BLM signal lasts 2 ms • 2.4 x 104 words (2-bytes)/sec/BLM • Only selected BLMs send full data (10 max for entire system) • Sum of losses per BLM per macro-pulse to be sent • Slow – 16 bits (incl sign), 10 kSa/s • 2 x 104 words (2-bytes)/sec/BLM • Only sum or average per second required • Controls • Gain per channel • Loss threshold (2 per channel) • Loss trip bits (2 per channel) • Mask bits (2 per channel) • Set and readback of High Voltage, On/Off bits Gain and calibration data folded into resolved data. SNS Beam Loss Monitor

  23. Photo-Multipliers • 1 point/ns (1 GS/s, 8 bits) • Controls supplied Fast ADC. • Data transferred to high level via Channel Access. SNS Beam Loss Monitor

  24. Beam Loss Waterfall RHIC BLM data SNS Beam Loss Monitor

  25. SNS BLM System - Summary • We are in the preliminary design stage. • Expected signals are well within the range of the proposed • detectors. • Electronics will be designed to measure high level losses over a • few turns, as well as low level losses over several cycles. • Integrated signal (weighted) sum over all detectors to compare • with the 1W/m criteria. • Every channel has adjustable thresholds and masks for the • Beam Abort System. SNS Beam Loss Monitor

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