1. 1 CCAT Instrumentation G.J. Stacey Cornell University

2. 2 Outline  Instrument Requirements  Need to make compromising decisions that deliver science most efficiently  Baseline Instruments – first light  Short submm camera  Near mm – wave camera  Extragalactic Spectrometer  Each needs this section is not to be include in July talk  Motivation  Implementation including: optical design, arrays, cooling,…  Instrument Envelopes including: Mass, Volume, Power, and Peripherals  Timelines for development  Cost estimates  Observing strategies  Lab facilities  Second light and future instrumentation

3. 3 Instrument Requirements  Primary science  Survey of distant star forming galaxies  Star and planetary system formation  Sunyaev-Zeldovich Effect  Exploration of the Kuiper Belt  The first three require a submm camera, and near mm wave camera  5’ x 5’ FOV  Operation in the 200, 350, 450, and 620 um bands  At least Nyquist sampled at 350 um  The last requires a near mm-wave camera operating at 850 um and 1.1 mm  Requirements – Sunil  The science of the survey is greatly improved by the addition of a submm spectrometer optimized for extragalactic line (searches?)  Requirements – Matt

4. 4 Submm Camera Decision Tree - FOV  The telescope delivers a 20’ FOV – why are we designing to a 5’ FOV?  The primary science can be delivered with 5’ FOV cameras  The telescope delivers a 1.17 meter image for a 20’ FOV – this is quite challenging to couple into a background limited camera  Current, and near future technology suggests 30,000 pixels is a reasonable goal for the array – this can deliver Nyquist sampled images over a 5’ x 5’ FOV at 350 um – to cover a 20’ FOV requires 500,000 pixels at 350 um…

5. 5 Decision Tree: Dichroic Operation?  Why not build a dichroic instrument that images in two bands, e.g. 350 and 850 um in a single cryostat  Excellent spatial registration  Enables SED science  However:  Sensitivities, and SEDs are not well matched:  Sources are detected (n) times faster at 850  m, does it make sense to continue integrating at 850 while awaiting the 350  m data? (needs support from science group)  The confusion limit is reached much faster at 850  m (need values from science group)  Plate scales are different, so that dichroic operation may well require f/# changes within the cryostat

6. 6 Decision Tree: Dichroic Operation?  Technology: A SCUBA-2 – like array appears to be the best bet in the short submm, while (TBD, Sunil) is likely better at the longer wavelengths  Fore-optics: excellent image quality and sensitivity is achieved in the short submm with a crystal quartz lens, but this system will increase background unacceptably at the longer wavelengths  Costs: the arrays are the largest single capital item for an instrument (a 30,000 pixel array is likely to cost > 3 M$) – folded into the different array technologies, it makes sense to construct separate cryostats

7. 7 Submm Photometer  First light instrument  FOV is 5’ x 5’  For Nyquist sampling at 350  m this requires a 170  170 pixel array  30,000 pixels, or 6 times that of SCUBA-2 (Question – doesn’t sound that aggressive….)  Primary bands are  200, 350, 450  m and 620  m  Driven by similar backgrounds and adequate sampling requirements  Filter wheel to change wavelengths

8. 8 Filter Wheel Operation  Backgrounds: Nyquist pixels at 350  m Wavelength Power NEP  850 um: 4.2E-13 Watts 0.3E-16 W-Hz -1/2  620 um: 2.1E-12 Watts 0.8E-16 W-Hz -1/2  450 um: 4.6E-12 Watts 1.2E-16 W-Hz -1/2  350 um: 9.5E-12 Watts 1.9E-16 W-Hz -1/2  200 um: 2.1E-11 Watts 3.6E-16 W-Hz -1/2  One can use the same array for work between 620 and 350  m, but either 850, or 200 will need to be left out (or the plate scale changed) – decision to take out 850 um capabilities (due to sensitivity – background from lenses – issue)

9. 9 Lens Reimager  f/8 delivered at a Naysmith focus  Investigated both mirror and lens designs  Mirror design maximizes through-put  Aberrations kept under control  However…  Mirror design requires 4 m class off-axis paraboloids  Dewar likely 8 m  3 m in size  For 5” FOV, the design is more modest  3 m class off-axis paraboloids  Dewar could be more modest 3 m  1.5 m in size

10. 10 Mirror Design  Optical design – not included since the file is huge  Could include both 20’ FOV and 5’ FOV designs…

11. 11 Transmissive Optics  System is much more compact  The instrument is ~ 1 x 1.5 m in size, with a 30 cm dewar window  However, selection of lens material is problematic – bulk absorption hurts you twice!  A first light camera with a 5’ FOV (still 30,000 pixels!) is “easy”

12. 12 Lens Parameters (to be shortened)  Requirements  Bring the entire FOV into the dewar window -- 20 cm  Provide for a cold Lyot stop to minimize thermal backgrounds  Deliver the proper plate scale – either 1 mm or 0.5 mm pixels  For near Nyquist sampling 200  m  f/4 (f*1.22 /2 = 0.5 mm)  Focal length = 80 cm  Deliver good image quality – diffraction limited  Found that a variety of materials will work  Selection criterion was essentially transmission  Index of refraction  radius of curvature – thickness of lens  Extinction coefficient, or transmission per cm thickness  Other important features  Material properties – environmental (water), structural (window)  Cost  AR coatable?

13. 13 Lens Materials Considered MaterialIndexExtinction Coefficient Radius of Curvature (cm) Thick- ness (cm) Trans- mission Polyethylene1.5060.12650.610.369% Sapphire3.20.912202.1338% Fused silica1.810.179816.059% Quartz2.1130.0891114.2883% Germanium4.0060.0733001.5693%

14. 14 Germanium Lens Design: 5’ FOV Instrument Envelope  This would accommodate a 300  300 (90,000) pixel array  The change in f/# means the second lens is smaller than the first – can use this as the dewar window 3.5 m Lens diameter ~ 35 cm Optical trace removed to limit file size

15. 15 Germanium Lens Design: 5’ FOV PSF removed to limit file size

16. 16 4 position filter wheel (e.g. 200, 350, 450, 620) Lyot stop diameter: 14 cm The Dewar 27 cm entrance window Array 5’  5’ FOV: 90,000 pixels Cryocoolers Heat Reflecting filters 1.1 m

17. 17 Array (Darren)  Baseline is extension of SCUBA-2 array  4 x (32x40) pixel subarrays to make 5120 pixels – extend to 30,000?  Is this feasible?  1 mm vs. 0.5 mm pitch  Detector NEP  Costs and delivery  Alternatives

18. 18 Photometer Budget – displayed as an example – other instruments just will have summary budgets  Total budget > 9.7 M$  Dominant items in the budget are salaries (6.7 M$), and the as yet undetermined price of the arrays (3 to ? M$)  5000 element SCUBA-2 array can be delivered for 1.4 M$ (or so)  Must have dramatic economies of scale (or new technology) to reach 1 million pixels (280 M$), or even 90,000 pixels (25 M$)

19. 19 Photometer Budget: Capital Equipment ItemCostComments Array3 to 15 M$1.4 M$ for 5000 pixel SCUBA-2 – Need to get bids during next phase In house manufacture – leverage off of space projects (e.g. SAFIR) Array Electronics0.5 M$In house manufacture… learning about this this summer with ZEUS Cryostat250 KBased on similar sized cryostats Filters/Optics250 KCardiff (Peter Ade) Fore-optics250 KWorking on this number Pulse tube cooler37 KCryomech Low-T cooler50 KChase Research

20. 20 Photometer Budget: Personnel PI/Co-PIElectrical Engineer Lead EngineerSoftware Engineer 2 Research AssociatesAdministrative Support 2 Mechanical EngineersGraduate Students Summer Students Total personnel800 K$/year + 33% fringe benefits Travel30 K/year (on average) Miscellaneous15 K/year Shipping30 K totals6 year build: 6.7 M$

21. 21 Long Wavelength Camera  Motivation – low background and systematics  Optics  Array technology  Costs estimates  Timeline

22. 22 Direct Detection Spectrometers Broad-band and wide-field imaging spectroscopy will be a unique niche of single-dish telescopes.  Bolometer array spectrometers cover N times more sky or bandwidth than ALMA can CO J=3->2 M. Dumke et al. 2001 CO J=7->6 Bradford et al. 2003 16x16 array on CCAT ALMA Primary beam at 810 GHz Herschel beam at 810 GHz Example: nearby galaxies -- ALMA resolves out emission, while Herschel under resolves it

23. 23 Direct Detection Spectrometers for CCAT Broad-band and wide-field imaging spectroscopy will be a unique niche of single- dish telescopes. -> Bolometer array spectrometers cover N times more sky or bandwidth than ALMA can Suite of far-IR through mm-wave lines provide physical conditions and redshifts in dusty high-z populations -- broad bandwidth is required. CCAT spectrographs will be sensitive to z~5 ULIRGS. ISO LWS, Fischer et al 1999 Z-Spec first light at the CSO June 2005

24. 24 Strawman Spectrometers: Long-Slit Echelle Strawman -- 128 pixels in spectral dimension -- e.g. 0.86 mm pixels -- f/2.5 spectrometer, slightly oversampled Collimator must be oversized by 12 cm to accommodate angles off the grating! --> 30 cm diameter collimator --> grating 30 cm by 40 cm, to accommodate spatial throughput --> Grating and collimator approach of 1 meter in all dimensions -- Large but doable. 30 cm 40 cm 35 cm 816 micron pitch grating Layout from ZEUS -- Cornell -- Stacey et al.

25. 25 8 x 20 cm = 160 cm collimator focus Full field at f/8 -> 20 cm window Collimated beam + overheads: 25 cm dia (and etalon must be near pupil) Etalon spacing: few cm Faster final focal ratio (2-3) to accommodate large array Array up to 10 cm F-P field is limited by beam divergence at the longest wavelengths: R max ~D c 2 / lqD p For a 20 cm collimated beam and a 3.5 arcmin field (20 cm window and 128 2 at 450 mm), this means: R max =1850 at 450 um R max =990 at 850 um CCAT strawman F-P cryostat is 2 meters in longest dimension -- Large but doable. Layout from SPIFI -- Bradford, Stacey et al. 2001 Strawman Spectrometers: Imaging Fabry- Perot

26. 26 Polarizing grid Dichroics (soft edges OK) BLISS-SPICA WaFIRS suite for R~1000 at 40-600 microns. All fits within 100 x 100 x 50 cm envelope. WaFIRS Grating Modules Single point source spectrograph Broad bandwidth: 1:1.65 instantaneous 2-D medium -- compact and stackable Z-Spec R~200-400 at 1-1.6 mm Multiple modules can multiplex in position or waveband. So could cover multiple CCAT atmospheric windows simultaneously. 40cm

27. 27 Cryocoolers – Thomas  We are base-lining closed cycle refrigerators for all CCAT instrumentation  Sterling and Gifford-McMahon cycle coolers have moving parts on the cold head so that there are issues with vibrations  Pulse-tube coolers have no moving parts, so that these issues are minimized  The bolometers must operate with very stable base temperatures  The end stage coolers will be closed cycle 3 He systems or ADRs that provide both temperature stability, and are vibration free  The temperature isolation system should shield the cold head against the 4.2 K temperature fluctuations and residual vibrations.  The TES bolometers are less susceptible to microphonics than thermister sensed bolometers since they are low impedance devices

28. 28 Cryocoolers  Pulse tube coolers cool down instrument to 4.2 K  Closed cycle 4 He system cools detector package to 2 K  Closed cycle 3 He system cools detector package to 250 to 300m K  For the baseline photometer, the sensitivity is achievable with a head temperature of 225 mK  We get NEPs ~ 10 -16 W/Hz with Zeus at 250 mK  If necessary, ADR can cool system further (60 mK)

29. 29 Pulse Tube Cooler  Requires first stage temperature near 55 K, where it can dump 25 W (typically, radiation will add another 20 W to the budget)  Intermediate T coolers deliver 1 W cooling per 30 watts input power (require 1.2 K W for this cooler)  The pulse tube then can provide 0.7 W of cooling power at 4.2 K  Size of pulse tube cooler is compatible with the cryostats we envision Figure of cooler removed to minimize file size

30. 30 Low T Head  “He-7” system from VeriCold:  Based on 4K pulse tube cooler two stage 4 He and 3 He sorption coolers by Chase Research Cryogenic Ltd.  100 uW cooling @ 300 mK  Can go to 225 mK with “He-10” system:  Dual stage 3 He sorption cooler  50 uW cooling @ 250 mK in our ZEUS spectrometer  ADR  Typically has 3 He thermal shield  Provides ~ few uW cooling @ 60 mK Dual stage 3 He cooler used in ZEUS/SPIFI Figure of helium-6 system removed to minimize file size

31. 31 Photometer Cooler Summary  Pulse tube cooler from Cryomech  Cooling power of 0.7 W at 4.2 K  Power consumption ~ 7 KW  Price ~ 34 to 38 K$ including compressor (water or air cooled)  Low T cooler  Cooling power 75  W at 250 mK  Power consumption negligible  Price ~ 50 K$ for He-10 system

32. 32 Observing Strategies (Darren?)  Chopping  Scan stategies

33. 33 Pretty Pictures (TBD)  Sketch of photometer on Naysmith arm together with associated electronics, compressors, etc.

34. 34 Pretty Pictures (Gordon)  Sketch of multiple photometers on Naysmith arm to utilize larger FOV  This might include a prism, or just multiple lenses…

35. 35 Facility Laboratory (Simon)  Location  Requirements  Area  Power  Cranes  Test Facilities (pumps, spectrum analyzers, light sources, etc.

36. 36 The Next Generation  First light: 2 cameras and spectrometer  Second generation:  Heterodyne spectrometer  Polarimetry  Other types of direct detection spectrometers  40 um camera?  More distant future  Full FOV cameras