Download The RSS-NIR Detector System Progress

The RSS-NIR Spectrograph
Detector System Progress
Gregory Mosby, Jr.
RSS-NIR - PI Dr. Marsha Wolf
University of Wisconsin - Madison
NIR spectroscopy provides extensive
scientific opportunities.
Young/low mass stellar
evolution.
Obscured QSOs
GLIMPSE
Break age/Z degeneracy
Urrutia et al 2008
(ACS Composite
Images---I band for
red, g band for blue
and green)
Richards et al 2009
RSS-NIR designed as a prime focus
semi-warm instrument.
The RSS-NIR detector system
controlled with software from IUCCA.
-40 oC Pre-Dewar
Cryogenic Dewar
H2RG
+
MUX
4 Primary
Voltages
SIDECAR
ASIC
IUCAA
ISDEC
preamps
ADCs
FPGA
high speed USB interface
clock reset
flash memory
voltage regulators
6 Currents
5 Voltages
Many other options
Data
Acquisition
Computer
fiber optic link
RSS-NIR is using a Hawaii-2RG HgCdTe
detector.
Hawaii H2RG (2048x2048)
-HgCdTe
-1.7 µm cutoff
Teledyne
SIDECAR ASIC
-Optimized for 100 kHz
-Re-optimized for 200 kHz
IUCCA ISDEC controller
w/ IUCCA Software
NIR instrumentation has several
unique challenges:
NIR detector arrays have higher read noise than CCDs
Loose et al 2007
NIR instrumentation has several
unique challenges:
Thermal background is a critical constraint.
NIR instrumentation has several
unique challenges:
Persistence in NIR detector arrays must be minimized or calibrated.
Smith et al. 2005
Initial tests were completed in a test
dewar with engineering grade
detector.
Automated read noise testing was
used to help optimize noise to <20 e-.
Tests have begun with science
detector in cooled instrument dewar.
We have estimated the gain of the SG
detector to be slightly higher than
theoretically predicted.
Tackling the read noise
Fowler mode readout reduces noise by
factor of 2.
Up-the-ramp group should reduce noise
and help with saturation and cosmic rays.
Checking out the background.
Thermal background measurements
look promising.
Opaque
Cutoff
Clear
Empty
Persisting.
Initial persistence testing show a single
trap emission time constant of ~103 s.
Future work
Implement up-the-ramp algorithm for read
noise reduction.
Measure persistence decay time constants—as a
function of stimulus and relative intensity.
Measure improvements of up-the-ramp group
sampling and persistence calibration.
RSS-NIR Detector Properties
Characteristic
RSS-NIR (200 kHz)
CDS Read Noise (SIDECAR +IUCCA
board )
4.9 e-
CDS Read Noise (Full System, 18dB)
17.7 e-
Trap emission time constant
103 s
Measured Gain (18 dB)
2.4 e-/DN
Thermal background at -40 C (Cutoff
filter)
0.021 e-/s
Automated RSS longslit analysis (Ralf
Kotulla ) results of quasar host galaxies
Cosmic ray rejection algorithm
selection in development.
Flux calibration to follow as well.
Code will be publicly available after
testing.
Summary
Using diffusion k-means we make a
reduced basis set for stellar
population modeling.
Y
I1
We compared results of the DFK basis
set with those of the TB basis set on 6
different SFHs and 2 SFHs including
QSO light with synthetic data.
I2 O
1) DFK recovers values within 25% of the input A_V, and mass fraction in the Y,
I1, and O age bins (tie for I2) more often.
2) DFK has the fewest values outside of 100% (catastrophic failures) of the
input value for A_V and the mass fractions in all age bins.
Mosby et al 2015: http://arxiv.org/abs/1408.3335