Pascal Vincent, LPNHE Paris An advanced Facility for ground-based gamma-ray Astronomy CTA Paris...

Pascal Vincent, LPNHE Paris

An advanced Facility for ground-based gamma-ray AstronomyAn advanced Facility for ground-based gamma-ray Astronomy

CTA Paris meeting, 1-2nd march 2007

Camera and electronics

Manel Martinez and Pascal Vincent

on behalf of the

Camera Working Group

Robert Bazer-BachiStella Bradbury

Osvaldo CatalanoGerard Fontaine

Florian GoebelPhilippe Goret

German HermannEckart Lorenz

Manel MartinezRazmik Mirzoyan

Jelena NinkovicNepomuk Otte

Riccardo PaolettiBernard Peyaud

Michael PunchJoachim Rose

Thomas SchweizerJean-Paul TavernetMasahiro Teshima

Nicola TuriniPascal Vincent

CCherenkov herenkov TTelescope elescope AArrayrray




“… detection technique is well understood and very mature …”

“… design based on proven technology … … future upgrades possible.”

BBasic considerations asic considerations




30-50 telescopes10000 m2 mirror area

50 m2 photo sensitive area50k-100k electronics channels

Possibly mix of telescopes (5m, 14m, 28m)

LLayoutayout

with only factor of 10 in € ($, £, ¥ …)




Light concentrator and

Photon detector

Trigger Mechanics

Readout

TThe ccamera

Acquisition

Funding




PPhoton detectors

HEPPNeutrino

Air FluorescenceHEPP

Air shower

Cherenkov telescopes

Classical PMTClassical PMT

SiPMSiPM

HPDHPD

HEPP

IndustryIndustry

but aginglow gainhigh voltage…costcost

Promisingbut

R&DR&Ddark current

dynamiccrosstalk

…

Better QE, resolution …




PPhoton detectors

Traditional photomultipliers seem to be the most appropriate candidates for a design study. It’s a mature technology at low cost.

But the design of future cameras (electronics and mechanics) should take into account the possible success in new photon detector R&D. It should assume flexibility.

The photomultiplier technology is mature but nevertheless quite some improvements are possible.




Improvements of Classical PMT

a) Higher QE alkaline photo cathodes.b) Reduction of after pulses. c) Improved electron optics in the PMT (photoelectron collection efficiency, uniform gain over the first dynode

and very small transit time spread). d) Better separation of single photoelectron from system noise. e) Operation at lower gain (2-5x103) by a low number of dynodes in order to cope with high background light

levels and to reduce aging effects (operate during partial moonshine). High quality preamps to compensate for the low gain of few dynode PMT

f) Dynode structures to conserve very narrow pulse structures (pulses with < 1 nanosecond FWHM)g) Compact geometry with hemispherical cathodesh) Lowering of the necessary HV for a fixed gain (by increasing the gain/dynode) and use of low power consumption

HT units nevertheless able to provide reasonably high peak pulses.i) Smart HV controllers to protect automatically against adverse high level light backgroundj) Integration of peripheral electronics (HV, divider, preamp) to compact units of low power in order to decrease the

camera power and the needed cooling power and zero background emission causing EMI on neighboring elementsk) Improvement of peripheral increase of the QE by means of scattering lacquer coatings or other means of cathode

window surface treatment to enhance the chance of multiple photon passage of semitransparent photo cathodes.l) Making secondary surfaces highly reflective in the front-end area m) Minimization of backscatter losses of the first dynode.n) …

PPhotoMultiplier Tubes




IImprovements of Classical PMTmprovements of Classical PMT

2’’2’’ 2’’2’’ 3’’3’’

Some progress has been achieved recently

Tested by MPIK Munich




IImprovements of Classical PMTmprovements of Classical PMT

ClaimsClaims




Enhance the photon conversion by shifting wavelength to more efficient bandwidth region.

WWavelengthavelength shiftersshifters




Needed : development of light collectors with practical enhanced reflectivity and nearly zero dead area between pixels.

LLight concentrator

Light collector reflectivity 85 %Angular cutoff corresponding to the size of the mirrorActive area coverage >95%




EElectronicslectronics

Assuming 50k-100k channels readout electronics:

Pulse shape information readout window, time of signal arrival, amplitude/charge of the signalDigitization number bits does match 5 000 photo-electron dynamic rangeSingle photo-electron resolution peak/valley ≥ 1.5Dead time at 10 kHz few % (<10%)Input band width bigger than the pulse shape frequencySampling rate to be define with MC and measurement ?Crosstalk noElectronic noises much less than the single photo-electronElectronic power consumption = 3.1 W/channel Programmable triggerEnvironmental robustness yesStability of operation signal calibrated at 2%Temperature stabilityComplexity of installation few days to full performanceModularity -Reliability <5% dead channel with <10 person days maintenance per year Mass productionReproducibilityManpower for characterization and monitoring less than 2 persons€/channel (from PM to net) 500 – 1 000 € / channel +- ?…




RReadout technologyeadout technology

Mainly two proven solutions :

Trigger

GHz sampling analog memory

ADC

256-1024 ns memory depth

FIFO

Flash ADCDigital memory

μs … ms memory depth




New electronics components, specially dedicated to Cherenkov technique, are now developed and produced.

SAM (HESS II)Domino (MAGIC II)

Power consumption 300-35 mWAnalogue bandwidth 250-300 MHzDynamic range > 11 bitsIntegral non linearity < 1%Readout time 1.4 μs (for 16 ns signal)Crosstalk < 3‰Total noise 0.8 mV rmsMaximum readout frequency > 400 kHzSampling Frequency Range up to 4 GHzNumber of channels 2-10Number of cells 256-1024Maximum signal amplitude > 2 V

RReadout technologyeadout technology

More sophisticated ASIC are still under study to equip the front end part of the electronics.




TTriggerrigger

Different strategies have been developed

Sectors (HESS I)Cluster (MAGIC)

first Neighborssecond Neighbors

Sector + Neighboring (HESS II)

based on usage of comparator (HESS) or discriminator (MAGIC/SPC) for the treatment of the analogue signal. Simulations needed to define the most appropriated strategy.

Also dedicated chip has been developed for L1 and L2 triggering (HESS II).




AAcquisitioncquisition

Two different standards are currently used in Cherenkov technique.

CompactPCI (HESS)VME (MAGIC)

With the development of dedicated electronics cards.




MMechanicsechanics

Mechanics should be :

1. Compactbuilt and fully tested in a lab before installation on site (few days).

2. Modularity<5% dead channel with <10 person days maintenance per year.

3. Adapt new technology and photon detectors4. Low weight5. Cheap




MMechanicsechanics

Embedded camera with fully integrated electronics has advantages :

allows full construction and test in laboratorylocal treatment faster with integrated electronicsand minimize the signal distortionallows a complete monitoring and slow control of the systemlimit the number of connections facilitates the installation and maintenance

For light carbon structure telescopes new materials can be studied to reduce weight.

With camera unload facility one can imagine to have spare camera to allow regular maintenance.




CCostost

For a system of :

50 m2 photo sensitive area50k-100k electronics channels

Cost per channel should be of the order of 500 €, well above what we do. We can imagine 1 k€ for some units for more sophisticated data (pulse shape, timing information …).

Homogenous system or few design made from the same building blockMass production

Construction shared by many laboratories (opposite to Airbus)




LOILOI

ETCETC




CConclusionsonclusions

Optimization of design is needed:

1. Improvement of photomultiplier tubes (+ wavelength shifters). Light concentrators with better transmission. In parallel we may keep an eye on new photon detector.

2. Electronics :Development of new ASIC to integrate readout (analogue

memories + ADC + data buffering + …).Dedicated chip for trigger or other purpose.Define standard for acquisition design

3. Study of new materials for the mechanics4. Simulations (light collection, trigger, resolution …)

These studies could be achieved in a 2-3 years program.

The only R&D is for the cost.




Thank youThank you

CCherenkov herenkov TTelescope elescope AArrayrray

Robert Bazer-Bachi, Stella Bradbury, Osvaldo Catalano, Gerard Fontaine, Florian Goebel, Philippe Goret, German Hermann, Eckart Lorenz, Manel Martinez, Razmik Mirzoyan, Jelena

Ninkovic, Nepomuk Otte, Riccardo Paoletti, Bernard Peyaud, Michael Punch, Joachim Rose, Thomas Schweizer, Jean-Paul Tavernet, Masahiro Teshima,

Nicola Turini, Pascal Vincent

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Pascal Vincent, LPNHE Paris An advanced Facility for ground-based gamma-ray Astronomy CTA Paris...

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