Medipix2 meeting Dec. 2005

Medipix Activity at BerkeleyMedipix Activity at Berkeley

John Vallerga, Jason McPhate, Anton Tremsin

and

Bettina Mikulec

Medipix2 meeting Dec. 2005

ContentsContents

Tube Fabrication Progress– Header

– Body

– Medipix bake to 350 C

Neutron Detector Concept

Medium Infra-red ( = 5 m) APD array

Medipix2 meeting Dec. 2005

Image Tube progressImage Tube progress

Header assembly (interior)

Medipix2 meeting Dec. 2005

Image Tube progressImage Tube progress

Glued and wire bonded

Medipix2 meeting Dec. 2005

Image tube progressImage tube progress

Header assembly (exterior)

Medipix2 meeting Dec. 2005

Image tube progressImage tube progress

Tube body stackup before brazing

Medipix2 meeting Dec. 2005

High Temperature BakeHigh Temperature Bake

Vacuum bake Medipix2 mounted on ceramic header

Temperature profile to match tube processing

Class C Medipix2 chip (D9)

Initial bake to 300C for 10 hour (turbo failed)

Used DAC scans and threshold equilisation to characterize chip before and after bake.

No apparent change

Second bake 24 hours, with 10 hours at 350C.

Again no apparent change

Medipix2 meeting Dec. 2005

Neutron sensitive MCPsNeutron sensitive MCPs

Glass microchannel plates with 10B as a major dopant

Manufactured by Nova Scientific (Sturbridge Mass., USA)

High thermal neutron cross section

High spatial resolution as range of daughter products ~ 3 to 4 m in glass

Can also be made with Gd203 dopant and used as a passive collimator

Medipix2 readout useful for high flux, fast tomography

Medipix2 meeting Dec. 2005

10B neutron capture reaction10B neutron capture reaction

10B(n,)7Li reaction =3837 barns for thermal neutrons

and 8500 for cold neutrons

Medipix2 meeting Dec. 2005

Neutron capture reactionNeutron capture reactionn

7Li4He

n

Secondary electrons

10B

Secondary electrons

10B(n,)7Li reaction, =3837 barns

Medipix2 meeting Dec. 2005

Angular selective neutron detectionAngular selective neutron detection

Secondary electrons

Secondary electrons

No bias applied to front MCP

Angular selective

Bias applied to front MCP

All neutrons are detected

Medipix2 meeting Dec. 2005

Infra-red sensitive Medipix!Infra-red sensitive Medipix!

APD arrays seem a natural match to Medipix style readout

High optical QE, no vacuum tube!

Difficult mechanical/fabrication issues

– Backside illumination

– Optical and electrical crosstalk between pixels

– High excess noise factors

DRS technologies has a new HgxCd1-xTe process that can solve many of these issues concurrently and might be a good match to Medipix

– Medium infra-red sensitive

– Gain of 1000 ± 31

Medipix2 meeting Dec. 2005

MWIR APD Arrays MWIR APD Arrays

DRS Technologies

Medipix2 meeting Dec. 2005

APD Gain vs BiasAPD Gain vs Bias

= 4.3 m, 77K = 2.2 m, 273K

Medipix2 meeting Dec. 2005

Excess Noise FactorExcess Noise Factor

Medipix2 meeting Dec. 2005

Status of ideaStatus of idea

Preliminary discussions with DRS found no obvious problems

Sensor has high dark current so must be operated at 77º K

Questions

– Can Medipix2 operate at this low temperature

– Is Medipix2 a strong source of IR radiation

Applications

– Best IR sensors have ~6 e- readout noise at slow rates

– Adaptive optics tip/tilt sensors, wavefront sensors in science bandpass

– High frame rate IR imaging