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Gatling Gun Beam Diagnostics and Instrumentation. David Gassner Gatling Gun Review June 28, 2012. Outline. Phase 1 diagnostics p hilosophy: Provide core diagnostics for the first beams, current and profile. Overview Beam and machine parameters, challenges Beam transport layout - PowerPoint PPT Presentation
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June 28, 2012
David Gassner
Gatling Gun Beam Diagnostics and Instrumentation
David Gassner
Gatling Gun ReviewJune 28, 2012
June 28, 2012
David Gassner
Outline
• Overview– Beam and machine parameters, challenges– Beam transport layout
• Current Monitors– Beam Integrating Current Transformer (ICT)– Cable Current Monitors
• Beam Profile Monitors– YAG Screen Viewer– Halo Detector
• Future Upgrades– Beam Position Monitor– Fast Current Transformer (FCT)– Pepper Pot
• Summary
Phase 1 diagnostics philosophy: Provide core diagnostics for the first beams, current and profile.
June 28, 2012
David Gassner
Beam and Machine Parameters
Electron Beam Parameters– Initial tests; 2 cathodes, 1 Hz operations– 2 beams ~ 15mm full with diameter at the profile monitor– 3.5nC charge per bunch– 1.5nS FWHM bunch length– Energy = 220 KeV
Challenges for instrumentation– 250kV potential voltages– Sensitive photocathodes
Vacuum 10-12 Torr range Bake out compatibility to 400C Outgassing and desorption concerns
June 28, 2012
David Gassner
Beam Transport Layout
GunCathodes
ProfileMonitor
Collector
Ceramic Break for HV
Beam CurrentTransformer230kV
Combiner Diagnostics stationis grounded
230kV Inside Collector cage
HaloDetector
June 28, 2012
David Gassner
Beam Current Transformer
Beam Line Device:
Bergoz off-the-shelf Integrating Current Transformer (ICT) 178mm ID, fits over 6” CF flange
Mounted around dedicated commercial ceramic breakGG transport beam pipe 3.67” ID
Removable copper image current shroud
Plan to bake beam pipe to 400C, will need coolingto ensure ICT does not exceed 150C.
Side View
Similar installation at C-AD
Detailed mechanical design not complete
June 28, 2012
David Gassner
Beam Current Transformer Electronics
Bergoz - Beam Charge Monitor (BCM) Integrate-Hold-Reset (IHR) electronics - Measure individual bunches & bunch trains- Integration gate width adjustable 0.1us to 7us Noise <1pC beam charge Calibrated
10kHz max individual bunch rate measurement
Planned beam intensity/bunch range100pC – 3.5nC
BCM-IHR Timing diagram
June 28, 2012
David Gassner
Cable Current Monitors
Beam makes 2 bends from gun photocathode to beam ICTPotential for measuring:
- Transport efficiency between gun, collector, and ground. - Beam losses - Cathode QE
These measurement present accuracy challenges (noise, matching, HV, etc…)Need to look at details, setting up some tests.
Monitor current pulses (3.5nC, 1.5nS) in cables at several locations.
Reasonable to pursuethis measurement?
ICT
June 28, 2012
David Gassner
Profile Monitor
GunCathodes
ProfileMonitor
Collector
Ceramic Break for HV
CurrentTransformer230kV
Combiner Groundedregion
200kV Inside Collector cage
HaloDetector
June 28, 2012
David Gassner
Transverse Profile Monitor – YAG:Ce Screen
Removable Optics Box
Virtual Resolution Target
Lens and CCD Camera
Semitransparentmirror
Linear Magnetic Actuator (2 position)
Transfer Engineering Inc.
PMM-Lite model
400C bake-out
YAG:Ce Screen 5cm diameter (4.5cm active)Thin coating on upstream side to bleed off chargeThickness = Few hundred microns
GigE CCD camera3-motor lens, zoom, focus, iris.Virtual target for optical
<100 microns optical resolution
Transverse beam size ~15mm round diameter Destructive measurement (low power)YAG screen normal to beamCopper mirror at 450 downstream
Electron Beam
Optics Box Courtesy Radiabeam
June 28, 2012
David Gassner
0 0.5 1 1.5 2 2.5 3 3.5 4 4.50
1
2
3
4
5
6
7
8
9
10
Pfeiffer [Pressure]
Varian [Pressure]
Current [uA]
Pres
sure
[1E-
8 m
bar]
Transverse Profile Monitor – YAG:Ce Desorption Concern
Q: Will we be able to see an image on the YAG screen without ruining the cathodes?
A: If our double bend inhibits ion movement similar to the 270o bend at Mainz then we hope to tolerate a few uA’s on the YAG screen and not damage the cathodes.
270o bend
YAG Screen(~10-8 torr)
Pressure Rise vs. Current on YAG screen Igor Alexander, B2/Mainz
Gun (~10-11 torr)
Mainz PKATTest Source
Mott Pol.
Source: B2/Mainz
Pressure doubles with 3uA on YAG, in 10-8 torr range
June 28, 2012
David Gassner
Halo Detector
GunCathodes
ProfileMonitor
CollectorCeramic Break for HV
CurrentTransformer230kV
Combiner Groundedregion
230kV Inside Collector cage
HaloDetector
June 28, 2012
David Gassner
Halo Detector Profile Monitor – Upstream of Collector
Collector230kV
Isolated molybdenum jaws- Quad configuration- Need shield from collector (not designed yet)
Electronics:Gated integrator
Signal processing on HV platform:Fiber optic connection to transfer data
Protect electronics from arcs.
Halo DetectorsQuad split (230kV)
Grounded shieldRaw signals from similar E-Lens Quad
Halo Detector, beam offset (green & red)
E-Lens Quad Scraper
ElectronRepeller (260kV) Ceramic
Break
June 28, 2012
David Gassner
Future Upgrades
Fast Current Transformer (can be installed along side of ICT)Measure individual bunch charge in bunch trains300ps rise time, 1GHz bandwidthCalibrated measurement, Fast scope DAQTrack charge evolution (QE) for each cathode
Beam Position MonitorMeasure bunch center of mass positions (when combiner field is rotating)Need space in beam transport for pick-upHigh temperature (400C) pick-up design
Pepper Pot Emittance MeasurementA preliminary design: Normalized emittance: xn/yn= 20.5µm/20.1µmSlit width: 1 mm, slit space: 1.5 mm (~ 5 beamlets)Drift space: 0.1 m < L < 0.3 m upstream of YAG profile monitorThickness: 1 mm (Tungsten, SS, or copper)Use horizontal and vertical slits one on upper part, one on lower part of the mask.
Toroid widthsICT = 32mm
FCT = 22mm
Side View
June 28, 2012
David Gassner
Summary
• Core Diagnostic for Phase 1– Proof of principle, 2 cathodes, 1Hz 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)