Special Focus Workshop

“Towards 10 ps single soft photon detectors”

2013 IEEE NSS/MIC/RTSD SeoulSunday Oct 27, 2013

A very successful soft photon detector: the Photomultiplier (1934)

- ‘good’ quantum efficiency- rather fast- low noise @ high gain: very sensitive- little dark current, no bias current- radiation hard- quite linear

- voluminous & heavy- no position resolution- expensive- quite radioactive- can’t stand B fields

Amplification by multiplication: low noise!

Photo DiodeAvalanche Photo Diode APDSingle Photon Avalanche Diode SPADGeigerMode Avalanche Photodiode GM-APDDigital Photo Counters

The Silicon PhotoMultiplier: SiPM

Si-PMs are now in the focus:

Efficiency: potentially 100 %but: pixelizing reduces efficiency (borders)

Flat, thin, light, cheapCapable to stand strong B-fieldNoise, afterpulsing, recovery timeBest possible time resolution……?

MCP (invacuum)

John Vallerga: TimePix + MCPs

We do not know how to make MEMS made MCPs.Problems: aspect ratio of holes, ion back flow, acceptance

Use a MicroChannelPlate MCP?

Quantum Limited Imaging Detectors, RIT 2009, John Vallerga, jvv@ssl.berkeley.edu

The transmission dynode: ultra thin (20 - 100 nm) layers

diamondSiNitride (Si3N4) Si doped (SiRichNitride, SRN)CsIdoped SiO2

In vacuum: no gaseous detector………..

- ultra fast (single electron) detector: σ = 10 ps- E-force much larger than Lorenz force: operates in B-field- radiation hard- low mass

In vacuum: no gaseous detector………..

Classical Photo Cathode: Quantum Efficiency (QE) ~ 40 % at max

Can this be largely improved?

Towards we ain’t there yet10 ps not quite an arbitrary goalsingle the ultimate sensitivitysoft ~ 1 eV: there are other photons (like 511 keV)photon a very fundamental particledetectors that is where we are here for

Have a good exchange of information!

At the end:

Provoking speakers:Paul LecoqGary VarnerJohn Smedley

bringing forward ‘aggressive’ thesis’ like:

‘with Si-PMs 10 ps time resolution may be feasible,but at the cost of a lot of noise’

‘Scintillators are too slow for applications in 10 ps detectors Contrarily, Cherenkov radiation becomes more important’

‘There is no fundamental limit for the QE of photo cathodes’