6/15/051 energetic cosmic ray events in sipin-h2rg-015 device lance simms
TRANSCRIPT
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Energetic Cosmic Ray Events in SIPIN-H2RG-015 Device
Lance Simms
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H2RG Device Layout
800 micron CdZnTe substrate
10 micron HgCdTe bulk
Supposedly not photo-sensitive
Photosensitive
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Electron-Hole Pairs in Substrate?
• Photoelectrons generated in substrate will diffuse and cause multiple events in bulk material
• This might lead to “Poofy Events” in Detector, i.e. events with large spatial extent
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H2RG-15 Dark Current Data
• Examined the following– 5 ramps, 125 reads, minimum time between
reads=10.7 seconds• At temperature of 37K
– 45 ramps, 250 reads, minimum time between reads=10.7 seconds
• 9 sets of 5 ramps at temperatures between 26-50K
• Total Exposure time ~ 127,000 seconds
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Analysis
1) Took difference between last reads of successive ramps at a given temperature
-should eliminate hot pixels and bias structure
2) Applied 2 separate search algorithms to flag large events (large > at least 5 pixels)
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1st Search for Large Events
>100 >100 >100
>100 >100 >100
>100 > 100 >100
*Units are in Counts
1st Algorithm only flagged hit if each pixel in 3x3 region registered >100 counts
For each region, a Gaussian Fit was applied to the encompassing 10x10 area &Returned
-Sigma -coordinates-Amplitude -background
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1st Search Results
Total=2407 events spanning 3x3 region
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1st Search Results
Total=2407 events spanning 3x3 region
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2nd Search Looked for symmetric patterns where pixelswhere greater than a certain threshold
n=1 n=2 …etc.
…….
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2nd Search Results
Threshold 4 5 6 7 8 9
100 3 7 3 3 1 0
40 8 4 3 4 2 1
20 50 6 2 4 2 2
10 123 7 2 4 0 4
5 197 8 1 4 1 4
*n=4 to n=9 are tabulated
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No events found with spatial extent > 20 pixels
Largest Events found ~19 pixels wide (SNR ~ 2)
Background ~ 5 counts All pixel values above 10 counts
Overall Results
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Comparison with other H2RG images
Image courtesy of Roger Smith
Large Events likethe ones in this imagenot seen (or at leastnot detected)
Signal to Noise Ratioof circled events unknown
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No events of this typedetected.
Either search algorithm should haveflagged such an event.
Comparison with other H2RG images
Central Region: 5x noise~2400 pixels Image Courtesy of Amy Mainzer
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Possibilities for lack of large hits
• Particles that constitute these events might not make it into basement where IDTL is located (Steel girders)?
• Search criteria need to be modified (i.e. look for large events based on comparison to local noise rather than threshold)?