Gatling Gun Beam Diagnostics and Instrumentation David Gassner
Gatling Gun Beam Diagnostics and Instrumentation David Gassner Gatling Gun Review June 28, 2012 David Gassner June 28, 2012
Outline Phase 1 diagnostics philosophy: Provide core diagnostics for the first beams, current and profile. • Overview – – • Current Monitors – – • YAG Screen Viewer Halo Detector Future Upgrades – – – • Beam Integrating Current Transformer (ICT) Cable Current Monitors Beam Profile Monitors – – • Beam and machine parameters, challenges Beam transport layout Beam Position Monitor Fast Current Transformer (FCT) Pepper Pot Summary David Gassner June 28, 2012
Beam and Machine Parameters Electron Beam Parameters – – – Initial tests; 2 cathodes, 1 Hz operations 2 beams ~ 15 mm full with diameter at the profile monitor 3. 5 n. C charge per bunch 1. 5 n. S FWHM bunch length Energy = 220 Ke. V Challenges for instrumentation – 250 k. V potential voltages – Sensitive photocathodes § Vacuum 10 -12 Torr range § Bake out compatibility to 400 C § Outgassing and desorption concerns David Gassner June 28, 2012
Beam Transport Layout 230 k. V Beam Current Transformer Profile Monitor Ceramic Break for HV 230 k. V Inside Collector cage Gun Combiner Cathodes Diagnostics station is grounded Halo Detector Collector David Gassner June 28, 2012
Beam Current Transformer Beam Line Device: Side View Bergoz off-the-shelf Integrating Current Transformer (ICT) 178 mm ID, fits over 6” CF flange Mounted around dedicated commercial ceramic break GG transport beam pipe 3. 67” ID Removable copper image current shroud Plan to bake beam pipe to 400 C, will need cooling to ensure ICT does not exceed 150 C. Detailed mechanical design not complete Similar installation at C-AD David Gassner June 28, 2012
Beam Current Transformer Electronics Bergoz - Beam Charge Monitor (BCM) Integrate-Hold-Reset (IHR) electronics - Measure individual bunches & bunch trains - Integration gate width adjustable 0. 1 us to 7 us Noise <1 p. C beam charge Calibrated 10 k. Hz max individual bunch rate measurement Planned beam intensity/bunch range 100 p. C – 3. 5 n. C BCM-IHR Timing diagram David Gassner June 28, 2012
Cable Current Monitors Beam makes 2 bends from gun photocathode to beam ICT Potential for measuring: - Transport efficiency between gun, collector, and ground. - Beam losses - Cathode QE Monitor current pulses (3. 5 n. C, 1. 5 n. S) in cables at several locations. ICT Reasonable to pursue this measurement? These measurement present accuracy challenges (noise, matching, HV, etc…) Need to look at details, setting up some tests. David Gassner June 28, 2012
Profile Monitor 230 k. V Current Transformer Profile Monitor Ceramic Break for HV 200 k. V Inside Collector cage Gun Combiner Cathodes Grounded region Halo Detector Collector David Gassner June 28, 2012
Transverse Profile Monitor – YAG: Ce Screen Lens and CCD Camera Transverse beam size ~15 mm round diameter Destructive measurement (low power) YAG screen normal to beam Copper mirror at 450 downstream Linear Magnetic Actuator (2 position) Transfer Engineering Inc. PMM-Lite model 400 C bake-out Virtual Resolution Target Removable Optics Box Semitransparent mirror YAG: Ce Screen 5 cm diameter (4. 5 cm active) Thin coating on upstream side to bleed off charge Thickness = Few hundred microns Gig. E CCD camera 3 -motor lens, zoom, focus, iris. Virtual target for optical Electron Beam <100 microns optical resolution Optics Box Courtesy Radiabeam David Gassner June 28, 2012
Transverse Profile Monitor – YAG: Ce Desorption Concern Q: Will we be able to see an image on the YAG screen without ruining the cathodes? Pressure Rise vs. Current on YAG screen Igor Alexander, B 2/Mainz 12 Pressure doubles with 3 u. A on YAG, in 10 -8 torr range Pressure [1 E-8 mbar] 10 8 A: If our double bend inhibits ion movement similar to the 270 o bend at Mainz then we hope to tolerate a few u. A’s on the YAG screen and not damage the cathodes. Mott Pol. 6 Pfeiffer [Pressure] Mainz PKAT Test Source Gun (~10 -11 torr) 4 Varian [Pressure] 2 270 o bend 0 0 1 2 3 Current [u. A] 4 5 YAG Screen (~10 -8 torr) David Gassner Source: B 2/Mainz June 28, 2012
Halo Detector 230 k. V Current Transformer Profile Monitor Halo Detector 230 k. V Inside Collector cage Gun Combiner Cathodes Grounded region Ceramic Break for HV Collector David Gassner June 28, 2012
Halo Detector Profile Monitor – Upstream of Collector Halo Detectors Quad split (230 k. V) Isolated molybdenum jaws - Quad configuration - Need shield from collector (not designed yet) Electronics: Gated integrator E-Lens Quad Scraper Signal processing on HV platform: Fiber optic connection to transfer data Collector 230 k. V Protect electronics from arcs. Raw signals from similar E-Lens Quad Halo Detector, beam offset (green & red) Ceramic Break Grounded shield Electron Repeller (260 k. V) David Gassner June 28, 2012
Future Upgrades Beam Position Monitor Measure bunch center of mass positions (when combiner field is rotating) Need space in beam transport for pick-up High temperature (400 C) pick-up design Side View Fast Current Transformer (can be installed along side of ICT) Measure individual bunch charge in bunch trains 300 ps rise time, 1 GHz bandwidth Calibrated measurement, Fast scope DAQ Track charge evolution (QE) for each cathode Toroid widths ICT = 32 mm FCT = 22 mm Pepper Pot Emittance Measurement A preliminary design: Normalized emittance: xn/yn= 20. 5µm/20. 1µm Slit width: 1 mm, slit space: 1. 5 mm (~ 5 beamlets) Drift space: 0. 1 m < L < 0. 3 m upstream of YAG profile monitor Thickness: 1 mm (Tungsten, SS, or copper) Use horizontal and vertical slits one on upper part, one on lower part of the mask. David Gassner June 28, 2012
Summary • Core Diagnostic for Phase 1 – Proof of principle, 2 cathodes, 1 Hz operation § YAG: Ce Screen (Transverse profile, destructive, low power) § Quad Scraper (Near collector, halo monitor) § Current transformers (Bunched beam, and on cables) • Future Upgrades – More cathodes, higher frequency bunch trains § Beam Position Monitor (Non-destructive, fast) § Fast Current Transformer (Bunch charge in long trains) § Pepper Pot (Emittance, destructive) David Gassner June 28, 2012
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