Michal Szelezniak – LBL-IPHC meeting – 3-5 October 2007 MimoStar2 Current test results at LBL Update on recent tests of MimoStar2 sensors performed at

Michal Szelezniak – LBL-IPHC meeting – 3-5 October 2007

MimoStar2 Current test results at LBL

Update on recent tests of MimoStar2 sensors performed at LBL


22

Plans for testing MimoStar2 & MimoStar3

TESTING PLANS:– Preparations for testing of faulty pixels on MimoStar2

and MimoStar3 prototypes Possibility to stop on a pixel and test its sensitivity to external

signals (LED light)

– Currently no prototypes with faulty pixels are on hand– Test PCB for MimoStar3 has been submitted and is

expected to arrive in 2 weeks– In the mean time we could bond MimoStar2 and re-

verify if dead-pixels are related to handling (time constraints)


33

Testing modes/patterns

Static mode (stopping periodically on one selected pixel)

Dynamic mode (continuous readout and with acquisition of samples for the selected pixel only)

period

period: 84480 pixels

to DAQ


44

First tests of discharge time

No cooling in the system (no temperature control) Small protective box enclosing sensor and RDO board Pause on a pixel in the static mode limited to 3 frames

RESULTS:– Very short discharge time is static mode (~0.3 ms time constant) – Short discharge time in dynamic mode

STD ~ 23.2 ms (average) RAD ~ 11.0 ms (average)

Discharge time on the order of 100 ms was expected based on measurements performed in Strasbourg in the STATIC mode


55

Upgraded test system

Chiller and a radiator blowing cold air on the DUT

Large light-tight box containing the setup Infrared temperature sensor for continuous

temperature monitoring No restrictions on the programmable test

pattern– Duration of pause up to integral factors of 2×218

pixel selection pause on a pixel

frame extended due to the pause time arbitrry number ofcontinuous frames


66

Discharge time constant

@ 30 °C– STD 262 ms (average dynamic) 175 ms (static)– RAD 132 ms (average dynamic) 100 ms (static)

Consistent with results from Strasbourg

Measured in Strasbourg:

Time constant of 150 ms

(increases up to 1.16 s at -10°C)


77

Scan of the pixel array

Limitation of the system on continuous acquisition

– in full frame mode data set is limited to 5-6 continuous frames (due to RORC interrupts)

Only one pixel readout at a time

– But it can be scripted and looped

Room for improvement (more pixel per frame)

Could be implemented when a need arises (time constraints)

14 hrs of data taking


88

Pixel array uniformity

Information on uniformity of discharge time

uniformity on uniformity of leakage currents

Somewhat uniform (except for the first two rows

of pixel at the edge of the sensor – also visible with an oscilloscope)


99

Additional studies of equilibrium Tread/Tframe ↑ Vout ↑ frequency ↑ Vout ↓ Tread/Tframe ↑ time constant ↓During our recent phone conference (13Sep2007) Wojtek clarified that

practically the same equilibrium should be expected in both modes – this explains all of the above observations

If the readout phase “injects charge” (clock feed-through ?) and removes it at the end of the phase, we should be able to change the equilibrium in one pixel by stopping on it for an extended time

equilibrium

readout phase

readout phase

long pause on one pixel

not true when assuming different equilibria


1010

Conclusions on the self-biased structure

Voltage drop at the sensor output due to readout is 1.5 V => 500mV at the diode level

It’s the same equilibrium in all cases, especially in static and dynamic readout modes

equilibrium

Time constant

64 frames = 108 ms

Time constant

220 frames = 374 ms

LED

acquisition

frame

acquisition

frame

long pause on a pixel


1111

Reference frame Pause on a selected pixel

End pause and resume operation One frame after resuming operation


1212

Final remarks

Results prove that there is the same equilibrium in static and dynamic mode

Questions to designers:

Are there three columns active in each sub array at any given time (being prepared for readout)?

(This is just for better understanding of the operation of the MimoStar2 sensor)


1313

Hot pixels (1/3)


1414

Hot pixels (2/3)


1515

Hot pixels (3/3)

hot pixel regular pixel

Documents

Michal Szelezniak – LBL-IPHC meeting – 3-5 October 2007 MimoStar2 Current test results at LBL Update on recent tests of MimoStar2 sensors performed at