progress of mk.ii pepperpot: camera, scintillator and data analysis
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The Front End Test Stand Collaboration
Progress of Mk.II Pepperpot: Camera, Scintillator and
Data Analysis
Simon JollyImperial College
24th January 2007
24th January 2007 Simon Jolly, Imperial College 2
The Front End Test Stand Collaboration
Mk.II Improvements Over Mk.I
• Mechanical improvements (PJS).• Larger scintillator/pepperpot screen
for better coverage.• Scintillator that survives…• Faster camera with lower noise floor.• Improve data analysis.
24th January 2007 Simon Jolly, Imperial College 3
The Front End Test Stand Collaboration
Improved Data Analysis• Previous method: average weighted pixel
intensities from one spot to produce one point on emittance plot.
• New method: use every pixel, ray-tracing from hole centre.
• LOTS more data: 25 x 25 x 51 x 51 x 5 matrix (x, y, x’, y’, intensity, for every pixel at every hole location). Data analysis takes longer…
• Emittance histogram “regeneration” should not be necessary for Mk.II; not yet tested on expanded Mk.I data (still some teething troubles…).
24th January 2007 Simon Jolly, Imperial College 4
The Front End Test Stand Collaboration
New Camera• Current camera (PCO 2000) has some problems:
– Software unstable & limited (all data analysis in Matlab).– No signal amplification: need lots of light; can only integrate
whole pulses.– Noise floor artifically set at 100 counts: no low light sensitivity.– A number of other things we were unaware of when purchasing
camera…• With extra money, could we purchase a faster camera with
MCP?• Best option looks like Princeton/PIActon PIMAX 1300:
– <10ns gating.– 1340 x 1300 pixel resolution.– 20m x 20m pixels (twice as large as PCO).– Range of intensifier tubes.– VERY long delivery times on tubes (high demand from
Hamamatsu).
24th January 2007 Simon Jolly, Imperial College 5
The Front End Test Stand Collaboration
PI-MAX Intensifier QE Curves
Gen II
Gen III
Gen IIIfilmless
PCO
24th January 2007 Simon Jolly, Imperial College 6
The Front End Test Stand Collaboration
Intensifier Choices• Gen II gives broadest spectral response
but much lower QE.• Gen III filmless is the opposite: narrow, but
high QE.• Gen III gives better compromise, but
longest delivery times (US Military buying them all…).
• How quick do we need to order?• Measure scintillator first? Response looks
similar to PCO, plus Ce-doped quartz peaks at 395nm.
24th January 2007 Simon Jolly, Imperial College 7
The Front End Test Stand Collaboration
New Scintillator• Quartz has given best results so far:
– Virtually no degradation in light output.– Burn marks appear for pepperpot measurement, but
don’t affect light intensity.– Too slow for sub-pulse measurements (decay time
>100s).
• Looking for single 150mm x 150mm plate from several manufacturers.
• Heraeus most promising: can provide undoped and Ce-doped screen.
• Ce-doping should improve speed (80ns decay) and light output, but may affect radiation hardness…
24th January 2007 Simon Jolly, Imperial College 8
The Front End Test Stand Collaboration
Fast Scintillator• Quartz works for slow measurements
(integrating single pulse), but not fast.• Ce-doped quartz screens from Heraeus
used in previous GSI/Darmstadt experiment:– http://prola.aps.org/pdf/PRL/v85/i21/p4518_1
• However, doping may affect radiation hardness: doping sites make easy colour centres, reducing scintillation efficiency.
• May need fast, undoped scintillator: with new camera, can survive with lower light output. How about Sapphire?
24th January 2007 Simon Jolly, Imperial College 9
The Front End Test Stand Collaboration
Alignment• Need better method to measure
alignment/orientation and focal plane of scintillator.
• Previously used rulers mounted on support: many drawbacks…
• Using quartz/sapphire, can etch graticule on beam-side surface of glass.
• Use 3 x 3 grid of 3mm squares in centre of plate:
• Can now get orientation, scaling and focus.
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