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
Download The PPT/PDF document "OACt OAC OATs UV Photon Counting Mode" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
OACt
OAC
OATs
UV Photon Counting Mode
M.Uslenghi
IASF-Milano
Firenze, 29/9/2017
METIS Calibration Workshop
Slide2Photon 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
Slide3Photon 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...
Slide4Photon counting data 9/5/2017
source
METIS Calibration Workshop, Florence, 29/09/2017
M.Uslenghi - UV Photon Counting
4
Slide5Photon 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
Slide7Source image
analog
“photon counting”
Slide8Source profileMETIS Calibration Workshop, Florence, 29/09/2017M.Uslenghi - UV Photon Counting
8
FWHM analog=3.1
0.5
FWHM PC=1.60.1
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 ...
Slide9What’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