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.