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OACt OAC OATs UV Photon Counting Mode OACt OAC OATs UV Photon Counting Mode

OACt OAC OATs UV Photon Counting Mode - PowerPoint Presentation

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OACt OAC OATs UV Photon Counting Mode - PPT Presentation

MUslenghi IASFMilano Firenze 2992017 METIS Calibration Workshop Photon counting overview METIS Calibration Workshop Florence 29092017 MUslenghi UV Photon Counting 2 intensifier HV set to 10006000 V ID: 788264

counting photon workshop frames photon counting frames workshop uslenghi calibration florence 2017 metis data photons 2017m set source correctly

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Presentation Transcript

Slide1

OACt

OAC

OATs

UV Photon Counting Mode

M.Uslenghi

IASF-Milano

Firenze, 29/9/2017

METIS Calibration Workshop

Slide2

Photon counting overviewMETIS Calibration Workshop, Florence, 29/09/2017M.Uslenghi - UV Photon Counting

2

intensifier: HV set to 1000/6000 V

APS: DIT set to minimum (

∼0.1s)

centroiding

of the event spots -> improve resolution

Slide3

Photon counting acquisitionsMETIS Calibration Workshop, Florence, 29/09/2017M.Uslenghi - UV Photon Counting

3

The debugging of the software of the PC mode took time

On 29

th

April we carried out a test to evaluate achievable performance in photon counting (but with very limited statistics): acquisition of a set of images with the shortest exposure time (97 ms) and HV set to 1000/6000V and offline processing with a software emulator of the PCU

Only the very last day (9 May 2017) the photon counting mode was finally working. Measurements have been carried out under the pressure for wrapping up METIS, with no possibility for further investigations. There are problems...

Slide4

Photon counting data 9/5/2017

source

METIS Calibration Workshop, Florence, 29/09/2017

M.Uslenghi - UV Photon Counting

4

Slide5

Photon counting data 9/5/2017

clustering of background photons

the number of photons with identical coordinates is not consistent with the statistics. Photons with the same coordinates are detected in consecutive frames (even up to 20 frames). Amplitude is more or less constant

even the distribution of the photons close to the projected source is peculiar

METIS Calibration Workshop, Florence, 29/09/2017

M.Uslenghi - UV Photon Counting

5

Slide6

“Photon counting evaluation” 29/4/2017195 frames with DIT=97 ms

the median of the 195 frames used as offset mapframes analyzed offline with the IDL emulator of the PCU

the image obtained from the accumulation matrix (“Photon Counting”) has been compared to the image obtained by averaging the 195 frames (“Analog”)

METIS Calibration Workshop, Florence, 29/09/2017

M.Uslenghi - UV Photon Counting

6

Slide7

Source image

analog

“photon counting”

Slide8

Source profileMETIS Calibration Workshop, Florence, 29/09/2017M.Uslenghi - UV Photon Counting

8

FWHM analog=3.1

0.5

FWHM PC=1.60.1

the shape is peculiar, but similar in PC and analognot clear if there are the same problems in this dataset or not. Statistics is low ...

Slide9

What’s wrong?METIS Calibration Workshop, Florence, 29/09/2017M.Uslenghi - UV Photon Counting

9

suspect

possible explanation

why not

intensifierthe clustering is real, there are local micro-dischargesno evidence in the “analog” data

phosphor screen or APS

when a photon event occur, there is a kind of persistence

the intensity of the signal is low

this

“persistence” should last for up to 20 frames (2s)

the intensity of the spot does not decrease in consecutive frames (no decay)

PCUdata are good, but processing is wrong

the PCU has a memory depth of 2 rows (2048 pixels), there is no way it may “remember” information in subsequent frames

the logic has been widely validated on the FUMO

Memory bufferdata in the memory buffer are not correctly refreshed

the data have the right format, the frame tag are correctly numbered, the x-y-sum values are consistent with the expectation

Offset mapthe offset map is not correctly synchronized with the data

sent by the detectorwrong photon identification of noise peaks over-threshold not corrected by the (wrong) bias

further measurements with the spare or the QM model could discriminate between something due to the detector and something due to the MPPU