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HXD-PIN Noise

2012-04-03
Caution on the PIN noise increase

The leakage current of PIN sensors has been gradually increasing by the radiation damage. Therefore, the HXD team has released the PIN threshold level files (ae_hxd_pinthr_????????.fits) several times. This file is used to cut the noise events so that the clean event file does not contain the noise events. However, after releasing the threshold level files, the PIN noise level increased, and the noise events sometimes leak into the clean event files before the release of new threhols files, especially for observations where the HXD temperature was high. (The temperature can be checked at <http://www.astro.isas.jaxa.jp/suzaku/log/hk/>). In that case, the PIN noise events appear at 10--15 keV as a steep increase to the lower energy as shown in figure 1. HXD team is now updating the therehold files.


Fig 1: Example of the PIN spectrum with the noise contamination.


The noise contamination is identified when you look at the individual 64 PIN spectrum. The noise level is different among PINs, unlike the cosmic signals and background signals. In the XSELECT, the following command selects the events of individual PIN.

filter column "UNITID=2:2 PIN_ID=3:3"

This is the example to extract the event of PIN NO.3 of the Well UNIT 2. UNITID is in the range of 0...15 and PIN_ID is in the range of 0..3.

Figure 2 is an example of individual 64 PIN spectrum for the data with the noise contamination.



Fig 2: Emample of 64 individual PIN spectra with noise conamination.


The following are an example of the C-shell script for creating the 64 PIN spectrum and plotting them in the postscript files with XSPEC. This is just an example, so not necessarily supported for general cases.

#!/bin/csh
#


set ifile = pin_cl.evt.gz
echo $ifile


set unitid = 0
while ($unitid < 16)
set pinid = 0
while ($pinid < 4)

echo unitid=$unitid, pinid=$pinid

## extract PIN spectrum of individual PIN

xselect <<EOF
xsel

read events
.
${ifile}

filter column "UNITID=${unitid}:${unitid} PIN_ID=${pinid}:${pinid}"
extract events

extract spec
save spec
pin_u${unitid}p${pinid}

exit
no

EOF

@ pinid ++
end
@ unitid ++
end

#
# plot spectra
#
set unit = 0
while ($unit < 16)

xspec <<EOF
data 1:1 pin_u${unit}p0.pha
data 2:2 pin_u${unit}p1.pha
data 3:3 pin_u${unit}p2.pha
data 4:4 pin_u${unit}p3.pha
cpd /xw
plot ld

iplot
ra x 25 55
ra y 0.00001 0.01
lw 7
cs 1.3
la ti
la fo PIN unit ${unit}
time off
plot
hard pin_u${unit}.ps/cps
q

exit
EOF


echo $unit

@ unit ++
end


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