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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)?