CCD Mosaics at CTIO and SOAR.

Abstract: Mosaics based on 2K x 4K CCDs are briefly reviewed.  An 8Kx8K mosaic of SITe002A CCDs is in use at the 4m Blanco telescope.  At the SOAR 4.1 m telescope E2V 44-82 CCDs are used in an 4Kx4K Imager and another 4Kx4K mini-mosaic utilizing CCID20 detectors will be employed by the Goodman Spectrograph.  A 62 CCD mosaic incorporating high resistivity CCDs from LBNL is part of the Dark Energy Camera project that should be available at the 4m Blanco telescope by 2009. Each of these four types of 2K x 4K CCDs have two output amplifiers and 15 micron pixels.

4m BLANCO: 8K x 8K MOSAIC-2 (Imager).

2xCCD44-82 (E2V)3 edge buttable, CCD44-82s have an extra FET to buffer the output stage (hence 2 drain voltages). Setting V_OD too high causes amplifier glow. This CCD has two Outputs Gates and also a Dump Drain.

M83 This SOI 5x5 arcminutes color image, obtained on February 16th 2005, is composed of two sets of 0.7 arcsec FWHM images taken at the B, V and R filters. A 20 arcseconds shift was applied between the two sets of observations in order to eliminate the central gap of the CCDs mosaic in the final image.

SOAR IMAGER: 4k x 4k Mini-Mosaic of E2V CCDsA Mini-Mosaic made of two CCD44-82 detectors covers a 5.5 x 5.5 arcmin FOV at 0.08” / pix on the SOAR 4.1m telescope. It includes twin filter wheels -5 positions ea.- and a fast linear shutter. This Imager started operations in 2004.

MOSAIC-2 SOAR IMAGER GOODMAN SPECT. DECAM

8 three-side buttable SITe002A CCDs are used by Mosaic-2 to cover a FOV of 36’ x 36’, at a scale of 0.27”/ pix. Its shutter and a 14-filter track –running in a loop over the dewar top- are both pneumatically actuated. This wide field Mosaic Imager has been in regular use for the past 6 years at the 4m Blanco telescope and is typically scheduled 120 nights per year. Mosaic-2 is a copy of KPNO’s Mosaic-1. However to read out Mosaic-2 uses 16 channels whereas Mosaic-1 uses 8 channels. One Mosaic image represents 140 MB of data.

The peak QE for SITe002As is 85% at 600 nm; the CCDs run at -95 oC. Fringing is < 5% in the I band, there is some low level crosstalk which gets successfully removed, there are no after-images. Grounding: CCDs are wired to the corresponding Arcon star point -at the Arcon backplane (=multilayer planar PCB)- and are isolated from the detector mount and dewar.

Ricardo E. Schmidt, CTIO / NOAO SDW2005, Taormina.

Collimator

Articulated Camera

SOAR Goodman Spectrograph: P.I.: Chris Clemens (UNC).With Long-slit & Multi-slit capabilities it uses a 4k x 4k Mini-Mosaic and covers an effective FOV of 7.2’ diameter on SOAR, at a scale of 0.15” / pix. Observing will start in 2005.

CCID20

This system is optimized for the UV/Blue.The CCID20 requires sequencing of reset and drain voltages on power up and power down: of the two, the output drain should be the last to be turned on and the first to be turned off.

The CCID20 uses high resistivity bulk silicon thinned to 40 µm and hence there is an asociated red QE boost and less fringing due to larger thickness. This 3 side buttable CCD is back-illuminated but not MPP.

For the CCID20 we get a lowest noise of 1.9 e- at a conversion gain of 0.4 e- / ADU. We treated the CCID20 with dry air plus heat to solve some cosmetic problems and to get an increased QE.

NOAO’s Monsoon controller will be used to read out the 62 CCDs. 18 CCDs will be treated as “6 groups of 3”, with the assumption that the same clock rails can be applied to groups of 3 CCDs. oTCCD will be read for each CCD and used for QE corrections.

Dark Energy Camera, a collaboration-lead by Fermilab- to build a 62 CCDImager. DECAM will be used for a 5000 sq. deg. survey to constrain the Dark Energy parameter w to ~ 5%.DECAM observing to start in 2009.

LBNL high resistivity, n-type silicon CCD which can be fully depleted. Clock and bias voltages are reversed in sign from conventional CCDs. This 4 side buttable, back illuminated CCD has a QE> 50% at 1000 nm. These CCDs: 1) Use a buried p-channel 2) Use substrate bias voltage to fully deplete substrate and control PSF 3) Require special erase procedure The CCDs will be packaged by Fermilab.

A scroll shutter design is being tested.

Frontendelectronics

Feed through bd.

The DECAM instrument will replacethe Blanco 4m Prime Focus Cage

DewarShielded cableSDSU-2 ctrlr.

Heat exchanger

8K x 8K Mosaic

Dewar and four ARCONs shown

Controller

62 CCD Imager, FOV = 2.2 deg diamand active area diameter = 448 mm, @ 0.27”/pix on 4m Blanco PF.

2 x CCID20 Cryotiger

DECAM on 4m BLANCO

A LabVIEW based GUI calledArcVIEW is used with this Imager. ArcVIEW uses a Client / Server scheme andruns in a Linux environment on a PC.

An image binned 4x4 is read out in 6 sec (@ RON of 3.8 e).

2Kx4K

2Kx4K

2Kx4K

2Kx4K

2Kx4K

2Kx4K

2Kx4K

2Kx4K

One Arcon At the telescope images show fringing of < 2% in the I band. No after- images are seen.

2K x 4K CCDs with 15 micron pixels 8 x SITe 002A 2 x E2V CCD44-82 2 x MIT/LL CCID20 62 x LBNL 2Kx4K

CCD technology (all w. 2 output amps) Thinned, n-channel Thinned, n-channel Hi Rho (40 µm), n-chan. Hi Rho (250 µm), p-chan.

Controller 4 x ARCON SDSU-2 SDSU-2 4 x MONSOON

Video boards (total) 4 @ 4 channel ea. 2 @ 2 channel ea. 2 @ 2 channel ea. 12 @ 12 channel ea.

Controller – Dewar connection Direct (connector–connector) 0.5m cable 1.2m cable

Electronics inside dewar None None None t.b.d.

Shared signals LGA/B ,H+SW rails per 1/2H-reg RGL/R, DD/RDL per H-reg RG per H-reg, PU/L per CCD Clock rails per 3 CCDs

Detector cooling Radiative/conductive, LN2 LN2 Cryotiger

Detector issues Slow parallels => long readout PSF = f (V_backside_bias =< 80V)Output amp glow for high V_OD Treat to improve QE and cosmetics

Cryocooler

Controller cooling Passive Liquid coolant Liquid coolant Liquid coolant (rack)

Chip mount material; heater Invar; embedded pwr-Rs Al; emb. Nickel-Chromium wire Invar; 8x FETs on PCB Invar; pwr-Rs

Wiring inside dewar Constantan & Cu wires Wires (Constantan&Cu), flexConstantan & Cu wires flex

Times (dwell, pixel, readout) for bin 1x1 3.6 µs, 14 µs, 100s 1 µs, 3.7 µs, 20 s 1 µs, 3.7 µs, 20s 1 µs, 4 µs, 20s

CCD responsivity, RON 1.8 µV/e, 5.9 e @ 2.4 e/ADU 5 µV/e, 3.8 e @ 2 e/ADU 10 µV/e, 3.1e @ 2 e/ADU 3 µV/e, <10e

Typical biases: V_OD, V_RD, V_OG 25 V, 14.3 V, 2 V (VJD=26V) 23.2V,10V,-4.7VOG1 & -3.7VOG2 18.5 V, 12.7 V, -1 V -22 V, -12.5 V, 2.2 V

0.7m cable

DEWAR FOR

GOODMAN