WIYN 3.5m Observatory

Bench CCD Characteristics

Device Characteristics for STA1 compared to T2KA

Property	STA1	T2KA

Size (pixels)	2600 x 4000	2048 x 2048
Pixel size	12 microns	24 microns
Full Well	87500 electrons	??
Read Noise (overscan)
- High Gain	3.2 el	6 el
- Medium Gain	3.7 el
- Low Gain	4.3 el

Readout Times	Binned 1x1; 2x2
- High Gain	227 sec; 67 sec
- Medium Gain	140 sec; 45 sec
- Low Gain	97 sec; 34 sec
Conversion Gain
- High Gain	0.219 (el/DN)
- Medium Gain	0.438 (el/DN)
- Low Gain	0.876 (el/DN)

Dynamic Range (saturation/RN) (1x1)	17,000 (Gain=.22 e/DN)	??
Linearity	1% to 63,000 el	1% to 190,000 el 0.1% to 180,000 el
Usable Data Range	DN upper limit
	1% linearity; Full well
- High Gain	262,143 DN ; 262,143 DN
- Medium Gain	143,800 DN ; 200,000 DN
- Low Gain	72,000 DN ; 100,000 DN
Dark Current
for binning:	above background level at 152 K
- 2x1	1.40 el/2x1binned pix/half-hour
- 2x2	2.64 el/2x2binned pix/half-hour	4-5 el/pix/hour
- 4x2	4.88 el/2x1binned pix/half-hour

Comments:

Users should note the numbers in the"usable" range - at medium or low gains it is possible to saturate the output amplifier before hitting the maximum values allowed by the Analog-to-Digital Converter. When the amplifier saturates the data become terribly non-linear.
Although the dark current is very low, there are some "hot pixels" (for which dark current is much larger than their immediate neighbors) which can be corrected during the processing stage. We will be developing master dark frames based on large number of frames which can be scaled to reduced the affect of the hot pixels on the science data. The hot pixels were checked and seem to behave as linear as other pixels over signal levels corresponding to the range 4700 electrons to 74000 electrons.
N.B. Be sure to leave the system running with the MOP gui visible at all times. When the one exits the MOP the clocks and control electronics are turned off. When the system is restarted after being powered down for any length of time, a residual charge remains on the CCD that looks like a weak signal. It takes several minutes in the powered on but idle state to clear this charge.
Fringing: there is fringing with this device longward of 7000 Å. A sample is reproduced below.

Measured Quantum Efficiency for STA1 T2KA and T2KC

T2KA QE Values (approx)

T2KC QE Values (approx)

STA1 QE Values (approx)

Expected spectral performance

BSC (f=285mm)
						T2KA		STA1
						24 micron pixels		12 micron pixels
Grating	l/mm	Blaze angle	Order	Blaze &lambda	Linear disp	Dispersion	Coverage	Dispersion	Coverage
				Angs	Angs/mm	Ang/pix	Angs	Ang/pix	Angs
316@7	316	7	1	7677	110.21	2.645	5417.0	1.323	5290.1
	316	7	2	3725	55.10	1.323	2708.5	0.661	2645.0
400@4.2	400	4.2	1	3537	87.48	2.100	4300.0	1.050	4199.2
600@10.1	600	10.1	1	5646	57.57	1.382	2829.8	0.691	2763.5
600@13.9	600	13.9	1	7734	56.77	1.362	2790.2	0.681	2724.8
	600	13.9	2	3867	28.38	0.681	1395.1	0.341	1362.4
860@30.9	860	30.9	1	11535	35.01	0.840	1720.8	0.420	1680.5
	860	30.9	2	5767	17.50	0.420	860.4	0.210	840.2
	860	30.9	3	3845	11.67	0.280	573.6	0.140	560.2
1200@28.7	1200	28.7	1	7730	25.65	0.616	1260.7	0.308	1231.1
	1200	28.7	2	3865	12.82	0.308	630.3	0.154	615.6
316@63.4	316	63.4	6	9388	8.29	0.199	407.4	0.099	397.8
	316	63.4	7	8047	7.10	0.170	349.2	0.085	341.0
	316	63.4	8	7041	6.22	0.149	305.5	0.075	298.4
	316	63.4	9	6259	5.53	0.133	271.6	0.066	265.2
	316	63.4	10	5633	4.97	0.119	244.4	0.060	238.7
	316	63.4	11	5120	4.52	0.108	222.2	0.054	217.0
	316	63.4	12	4694	4.14	0.099	203.7	0.050	198.9
	316	63.4	13	4333	3.83	0.092	188.0	0.046	183.6
	316	63.4	14	4023	3.55	0.085	174.6	0.043	170.5
VPH740	740	19.0	1	8798	44.8	1.076	2203	0.538	2152
VPH740	740	19.0	2	4399	22.4	0.538	1101.8	0.269	1076
VPH3300	3300	57.6	1	5120	5.69	0.137	279.7	0.068	273.1
N.B. the dispersion and the coverage of the VPH gratings depends on the exact angle at which they are used.

Simmons Camera (f=381mm - fewer fibers: see note below)
316@7	316	7	1	7450	82.44	1.979	4052.1	0.989	3957.1
	316	7	2	3725	41.22	0.989	2026.1	0.495	1978.6
400@4.2	400	4.2	1	3537	65.44	1.571	3216.5	0.785	3141.1
600@10.1	600	10.1	1	5646	43.07	1.034	2116.8	0.517	2067.2
600@13.9	600	13.9	1	7734	42.46	1.019	2087.2	0.510	2038.3
	600	13.9	2	3867	21.23	0.510	1043.6	0.255	1019.1
860@30.9	860	30.9	1	11535	26.19	0.629	1287.2	0.314	1257.0
	860	30.9	2	5768	13.09	0.314	643.6	0.157	628.5
	860	30.9	3	3845	8.73	0.210	429.1	0.105	419.0
1200@28.7	1200	28.7	1	7730	19.19	0.460	943.0	0.230	920.9
	1200	28.7	2	3865	9.59	0.230	471.5	0.115	460.5
316@63.4	316	63.4	6	9371	6.20	0.149	304.7	0.074	297.6
	316	63.4	7	8032	5.31	0.128	261.2	0.064	255.1
	316	63.4	8	7028	4.65	0.112	228.5	0.056	223.2
	316	63.4	9	6247	4.13	0.099	203.1	0.050	198.4
	316	63.4	10	5623	3.72	0.089	182.8	0.045	178.5
	316	63.4	11	5111	3.38	0.081	166.2	0.041	162.3
	316	63.4	12	4686	3.10	0.074	152.4	0.037	148.8
	316	63.4	13	4325	2.86	0.069	140.6	0.034	137.3
	316	63.4	14	4016	2.66	0.064	130.6	0.032	127.5
VPH740	740	19.0	1	8798	33.5	0.805	1648	0.402	1610
"	740	19.0	2	4399	16.8	0.402	824	0.201	805
VPH3300	3300	57.6	1	5120	4.26	0.102	209	0.051	204
N.B. the dispersion and the coverage of the VPH gratings depends on the exact angle at which they are used.

For comparison, two simple plots of approximate relative responses of the 316@63.4 echelle grating are shown below. Overlaid are the transmission curves of appropriate orders sorting filters to indicate the possible wavelength coverages. [N.B. There are also several order sorting filters for bluer wavelengths. Consult the Hydra Manual for more information.]

For fainter targets where spectral resolving power is less critical, the 3300 VPH grating may be more efficient than the Echelle. Please consult the VPH grating information page for details.

The plot below is a sample of fringing for STA1 at around 7500 Å. Data from a single column of a quartz lamp flatfield exposure. (Overscan level subtracted.)

Observers working longward of 7000 Å should remember to take several flatfield images each time the configuration is changed.

Finally, because the STA1 CCD only has 2600 pixels of 12 microns each in the spatial direction, observers wishing to use the Simmons Camera instead of the BSC should be advised that apporximately 15 fibers corresponding to the top and bottom of the fiber foot are not imaged onto the CCD. Since there are also several broken fibers, there will only be a total of 66 usable fibers per configuration.

Two technical reports describing characteristics of the device and its performance while being characterized are available:

Detector Characterization Report from the University of Arizona Imaging Technology Laboratory, and
CCD Test Report from the NOAO MONSOON Group. [Note that the device is currently being run with a single (Right amp) amplifier readout.]