1. FP420 TOF- Past and Future TOF in ATLAS and CMS proposals The problem
The solution
How to build and regain credibility
Sebastian White,BNL
Dec.7, Manchester

2. Cerenkov approach
Amazing paper by Nagoya with Quartz radiator and MCPPMT in test beam
But FP420 is a very high rate experiment-ie 200Mhz(pe)/cm^2 and MCPPMT is definitely not a high rate device
Even for Nagoya, rate is a huge issue at Super-Belle and it’s at least an order of magnitude worse in FP420
Sebastian White,BNL
Dec.7, Manchester

3. Cerenkov approach(II)
The issues:
Rate limit-ie gain distortion from space charge
Lifetime=deterioration of photocathode
Easy to calculate with elementary knowledge of PMT’s and access to data-sometimes hard to corroborate
Some dreams of improvements with complicated surface physics,etc- doesn’t belong in a proposal
Should never have touched them in the first place
Sebastian White,BNL
Dec.7, Manchester

4. The radiator
FP420 has two solutions- gas and Quartz- not clear whether any point to using both
Both have issues
For Gas it’s segmentation and maybe edge and geometry
For quartz I know at least uniformity but certainly no final design.
Sebastian White,BNL
Dec.7, Manchester

5. Segmentation We have to deal with segmentation at 1034
Assume you are only willing to waste~1/4 of the luminosity
Then at 420 you don’t need segmentation
At 220 you have to associate Cerenkov hit with track for 2 tracks
Probably have same segmentation for both and clone detectors
Sebastian White,BNL
Dec.7, Manchester

6. Timing solution
Very hard to find one. Most said impossible,particularly if insist on Cerenkov.
Interesting non-Cerenkov solution-see below
Recently Japanese tried to find high rate alternative to MCP
Hybrid photodetectors interesting. Speed limitation in the target.
Developed new low capacitance high speed APD target.
About to become a Hamamatsu product. I am buying the first one. Pretty expensive.
Sebastian White,BNL
Dec.7, Manchester

7. Sebastian White,BNL
Dec.7, Manchester

8. Sebastian White,BNL
Dec.7, Manchester

9. Sebastian White,BNL
Dec.7, Manchester

10. The new tube
Physics of TTS not in APD or focusing. It is Photocathode thickness. Only 1psec for 10nm! But 30psec FWHM for a thick one.
So probably could have pretty big photocathode. But available 3mm,6mm,8mm probably ok. Discussing.
Rate tested to >100Mhz. Electronics limited.
We will build something better at BNL.
Sebastian White,BNL
Dec.7, Manchester

11. The new tube
Packaging ok but not optimal. But Hamamatsu says can break out tube.
Probably build better electronics anyway.
Lifetime: don’t know but Rehak(who was pretty skeptical) says it should be ok
CMS very interested in APD rad damage. Tested their thin APDs to 100Grad!
So pretty good chance that it works.
Sebastian White,BNL
Dec.7, Manchester

12. The radiator
Start from the ground up. Choice of material and geometry should be optimized.
Maybe Quartz. Problem of getting all those photons onto that little photocathode.
First clarify segmentation. Simple statistics. Probably 4.
Then develop several concepts- lenses and mirrors, parabolic mirror, light pipe- have a few solutions
Sebastian White,BNL
Dec.7, Manchester

13. How to build and test something credible
Radiator: my preference is to have it done by professionals who know something about optical properties of materials and optics-maybe Labsphere
Work with them on our application, acceptable dispersion,etc. They would know how to choose the right quartz, for example.
With state of the art optical simulation and good expertise build it right the first time instead of trial and error approach
Sebastian White,BNL
Dec.7, Manchester

14. Building it
The PMT: obviously with so much riding on it this has to be understood very quickly.
There are details like whether we can get the right photocathode material, what are the possible parameters wrt area, how quickly we can get at least one so we can say we’ve seen one and things about cost and delivery and.of course, radiation
Sebastian White,BNL
Dec.7, Manchester

15. Electronics Probably new preamp but maybe Hamamatsu ok.
All the rest- Krzysztof and Jim’s CFD, HPTDC, ref timing system, should be just fine
Sounds like pretty many channels (at least 32) but that is due to segmentation anyway
Sebastian White,BNL
Dec.7, Manchester

16. Resources Electronics beyond the preamp: Assume there are open issues.
Cabling, clock distribution and other infrastructure important
Possibly further studies of these tubes.BNL Instrumentation would be an asset.
Sebastian White,BNL
Dec.7, Manchester

17. The alternative
Why not try to do better than Nagoya? Their application is not the same as ours anyway.
If APD is so fast why go through the trouble of making photons, worrying about optics, then converting them to electrons and detecting them.
Just measure the protons directly. It’s better and cheaper.
And don’t have to deal with Hamamatsu any more.
Sebastian White,BNL
Dec.7, Manchester

18. APD’s Advanced Photonics and RMD interesting
Hamamatsu not interresting
Very fast in a variety of geometries
Prefer RMD 8x8mm. Just perfect for our segmentation.
Huge signals! Ie 25V for a particle.
Sebastian White,BNL
Dec.7, Manchester

19. Ru106(e-~3.546MeV) RMD-8x8, HV=1670V, e- Sebastian White,BNL
Dec.7, Manchester

20. Ru106(e-~3.546MeV) APhI-5, HV=1850V, e- Sebastian White,BNL
Dec.7, Manchester

21. Conclusion So maybe things aren’t all that bad-2 solutions
Sorry I couldn’t be there
Sebastian White,BNL
Dec.7, Manchester