The Multiwavelength Sub/millimeter Inductance Camera (MUSIC) is a four-band photometric imaging camera operating from the Caltech Submillimeter Observatory (CSO). MUSIC is designed to utilize 2304 microwave kinetic inductance detectors (MKIDs), with 576 MKIDs for each observing band centered on 150, 230, 290, and 350 GHz. MUSIC’s field of view (FOV) is 14′ square, and the point-spread functions (PSFs) in the four observing bands have 45′′, 31′′, 25′′, and 22′′ full-widths at half maximum (FWHM). The camera was installed in April 2012 with 25% of its nominal detector count in each band, and has subsequently completed three short sets of engineering observations and one longer duration set of early science observations. Recent results from on-sky characterization of the instrument during these observing runs are presented, including achieved map- based sensitivities from deep integrations, along with results from lab-based measurements made during the same period. In addition, recent upgrades to MUSIC, which are expected to significantly improve the sensitivity of the camera, are described.
We describe the Short Wavelength Camera (SWCam) for the CCAT observatory including the primary science drivers, the coupling of the science drivers to the instrument requirements, the resulting implementation of the design, and its performance expectations at first light. CCAT is a 25 m submillimeter telescope planned to operate at 5600 meters, near the summit of Cerro Chajnantor in the Atacama Desert in northern Chile. CCAT is designed to give a total wave front error of 12.5 μm rms, so that combined with its high and exceptionally dry site, the facility will provide unsurpassed point source sensitivity deep into the short submillimeter bands to wavelengths as short as the 200 μm telluric window. The SWCam system consists of 7 sub-cameras that address 4 different telluric windows: 4 subcameras at 350 μm, 1 at 450 μm, 1 at 850 μm, and 1 at 2 mm wavelength. Each sub-camera has a 6’ diameter field of view, so that the total instantaneous field of view for SWCam is equivalent to a 16’ diameter circle. Each focal plane is populated with near unit filling factor arrays of Lumped Element Kinetic Inductance Detectors (LEKIDs) with pixels scaled to subtend an solid angle of (λ/D)2 on the sky. The total pixel count is 57,160. We expect background limited performance at each wavelength, and to be able to map < 35(°)2 of sky to 5 σ on the confusion noise at each wavelength per year with this first light instrument. Our primary science goal is to resolve the Cosmic Far-IR Background (CIRB) in our four colors so that we may explore the star and galaxy formation history of the Universe extending to within 500 million years of the Big Bang. CCAT's large and high-accuracy aperture, its fast slewing speed, use of instruments with large format arrays, and being located at a superb site enables mapping speeds of up to three orders of magnitude larger than contemporary or near future facilities and makes it uniquely sensitive, especially in the short submm bands.
Many applications in cosmology and astrophysics at millimeter wavelengths — CMB polarization, studies of galaxy clusters using the Sunyaev-Zeldovich effect, studies of star formation at high redshift and in our local universe and our galaxy— require large-format arrays of millimeter-wave detectors. Feedhorn, lens-coupled twinslot antenna, and phased-array antenna architectures for receiving mm-wave light present numerous advantages for control of systematics and for simultaneous coverage of both polarizations and/or multiple spectral bands. Simultaneously, kinetic inductance detectors using high-resistivity materials like titanium nitride are an attractive sensor option for large-format arrays because they are highly multiplexable and because their high responsivity can render two-level-system noise subdominant to photon and recombination noise. However, coupling the two is a challenge because of the impedance mismatch between the microstrip exiting these architectures and the high resistivity of titanium nitride. Mitigating direct absorption in the KID is also a challenge. We present a detailed titanium nitride KID design that addresses these challenges. The KID inductor is capacitively coupled to the microstrip in such a way as to form a lossy termination without creating an impedance mismatch. A parallelplate capacitor design mitigates direct absorption, uses hydrogenated amorphous silicon, and yields acceptable two-level-system noise. We show that an optimized design can yield expected sensitivities very close to the fundamental limit from photon and recombination noises for two relevant examples: single spectral band designs appropriate for 90 and 150 GHz for CMB polarization and a multi-spectral-band design that covers 90 GHz to 405 GHz in six bands for SZ effect studies.
CCAT will be a 25m diameter sub-millimeter telescope capable of operating in the 0.2 to 2.1mm wavelength range. It will be located at an altitude of 5600m on Cerro Chajnantor in northern Chile near the ALMA site. The anticipated first generation instruments include large format (60,000) kinetic inductance detector (KID) cameras, a large format heterodyne array and a direct detection multi-object spectrometer. The paper describes the architecture of the CCAT software and the development strategy.
We present the status of MUSIC, the MUltiwavelength Sub/millimeter Inductance Camera, a new instrument for the
Caltech Submillimeter Observatory. MUSIC is designed to have a 14', diffraction-limited field-of-view instrumented
with 2304 detectors in 576 spatial pixels and four spectral bands at 0.87, 1.04, 1.33, and 1.98 mm. MUSIC will be used
to study dusty star-forming galaxies, galaxy clusters via the Sunyaev-Zeldovich effect, and star formation in our own and
nearby galaxies. MUSIC uses broadband superconducting phased-array slot-dipole antennas to form beams, lumpedelement
on-chip bandpass filters to define spectral bands, and microwave kinetic inductance detectors to sense incoming
light. The focal plane is fabricated in 8 tiles consisting of 72 spatial pixels each. It is coupled to the telescope via an
ambient-temperature ellipsoidal mirror and a cold reimaging lens. A cold Lyot stop sits at the image of the primary
mirror formed by the ellipsoidal mirror. Dielectric and metal-mesh filters are used to block thermal infrared and out-ofband
radiation. The instrument uses a pulse tube cooler and 3He/ 3He/4He closed-cycle cooler to cool the focal plane to
below 250 mK. A multilayer shield attenuates Earth's magnetic field. Each focal plane tile is read out by a single pair of
coaxes and a HEMT amplifier. The readout system consists of 16 copies of custom-designed ADC/DAC and IF boards
coupled to the CASPER ROACH platform. We focus on recent updates on the instrument design and results from the
commissioning of the full camera in 2012.
As a proof-of-concept, we have constructed and tested a cryogenic polarimeter in the laboratory as a prototype
for the MUSIC instrument (Multiwavelength Sub/millimeter Kinetic Inductance Camera). The POLOCAM
instrument consists of a rotating cryogenic polarization modulator (sapphire half-waveplate) and polarization
analyzer (lithographed copper polarizers deposited on a thin film) placed into the optical path at the Lyot stop
(4K cold pupil stop) in a cryogenic dewar. We present an overview of the project, design and performance
results of the POLOCAM instrument (including polarization efficiencies and instrumental polarization), as well
as future application to the MUSIC-POL instrument.
CCAT will be a 25 m diameter, submillimeter-wave telescope. It will be located on Cerro Chajnantor in the
Atacama Desert, near ALMA. CCAT will be an on-axis, Ritchey-Chrétien design with an active primary to
compensate gravitational deformations. The primary mirror will have 162 segments, each with ~0.5 × 0.5 m
reflecting tiles on a ~2×2 m, insulated, carbon-fiber-reinforced-plastic subframe. CCAT will be equipped with
wide-field, multi-color cameras and multi-object spectrometers at its Nasmyth foci. These instruments will cover
all the atmospheric windows in the λ = 0.2 to 2 mm range. The field of view at the Nasmyth foci will be 1°,
so CCAT will be able to support cameras with a few ×104 detectors (spaced 2 beamwidths) at λ = 1 mm to
a few ×106 detectors (spaced half a beamwidth) at λ = 350 μm. Single instruments of this size are probably
impractical, so we will break the field into smaller pieces, with a separate sub-field camera for each piece. The
cameras will require some relay optics to couple the fairly slow beam from the telescope to the detectors. A
reflective relay for 1° field of view is too large to be practical, so we plan to use a compact, cold, refractive relay
in each sub-field camera.
Detectors employing superconducting microwave kinetic inductance detectors (MKIDs) can be read out by
measuring changes in either the resonator frequency or dissipation. We will discuss the pros and cons of both
methods, in particular, the readout method strategies being explored for the Multiwavelength Sub/millimeter
Inductance Camera (MUSIC) to be commissioned at the CSO in 2010. As predicted theoretically and observed
experimentally, the frequency responsivity is larger than the dissipation responsivity, by a factor of 2-4 under
typical conditions. In the absence of any other noise contributions, it should be easier to overcome amplifier
noise by simply using frequency readout. The resonators, however, exhibit excess frequency noise which has been
ascribed to a surface distribution of two-level fluctuators sensitive to specific device geometries and fabrication
techniques. Impressive dark noise performance has been achieved using modified resonator geometries employing
interdigitated capacitors (IDCs). To date, our noise measurement and modeling efforts have assumed an onresonance
readout, with the carrier power set well below the nonlinear regime. Several experimental indicators
suggested to us that the optimal readout technique may in fact require a higher readout power, with the carrier
tuned somewhat off resonance, and that a careful systematic study of the optimal readout conditions was needed.
We will present the results of such a study, and discuss the optimum readout conditions as well as the performance
that can be achieved relative to BLIP.
Proc. SPIE. 7741, Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy V
KEYWORDS: Signal to noise ratio, Electronics, Clocks, Resonators, Interference (communication), Amplifiers, Field programmable gate arrays, Signal processing, Field effect transistors, Microwave radiation
This paper will present the design, implementation, performance analysis of an open source readout system
for arrays of microwave kinetic inductance detectors (MKID) for mm/submm astronomy. The readout system
will perform frequency domain multiplexed real-time complex microwave transmission measurements in order
to monitor the instantaneous resonance frequency and dissipation of superconducting microresonators. Each
readout unit will be able to cover up to 550 MHz bandwidth and readout 256 complex frequency channels
simultaneously. The digital electronics include the customized DAC, ADC, IF system and the FPGA based
signal processing hardware developed by CASPER group.1-7 The entire system is open sourced, and can be
customized to meet challenging requirement in many applications: e.g. MKID, MSQUID etc.
We will present the design and implementation, along with calculations and some measurements of the performance,
of the room-temperature and cryogenic optics for MUSIC, a new (sub)millimeter camera we are
developing for the Caltech Submm Observatory (CSO). The design consists of two focusing elements in addition
to the CSO primary and secondary mirrors: a warm off-axis elliptical mirror and a cryogenic (4K) lens. These
optics will provide a 14 arcmin field of view that is diffraction limited in all four of the MUSIC observing bands
(2.00, 1.33, 1.02, and 0.86 mm). A cold (4K) Lyot stop will be used to define the primary mirror illumination,
which will be maximized while keeping spillover at the sub 1% level. The MUSIC focal plane will be populated
with broadband phased antenna arrays that efficiently couple to factor of (see manuscript) 3 in bandwidth,1, 2 and each pixel on
the focal plane will be read out via a set of four lumped element filters that define the MUSIC observing bands
(i.e., each pixel on the focal plane simultaneously observes in all four bands). Finally, a series of dielectric and
metal-mesh low pass filters have been implemented to reduce the optical power load on the MUSIC cryogenic
stages to a quasi-negligible level while maintaining good transmission in-band.
MUSIC (the Multiwavelength Submillimeter kinetic Inductance Camera) is an instrument being developed for
the Caltech Submillimeter Observatory by Caltech, JPL, the University of Colorado, and UCSB. MUSIC uses
microwave kinetic inductance detectors (MKIDs) - superconducting micro-resonators - as photon detectors. The
readout is almost entirely at room temperature and is highly multiplexed. MUSIC will have 576 spatial pixels
in four bands at 850, 1100, 1300 and 2000 microns. MUSIC is scheduled for deployment at the CSO in the
winter of 2010/2011. We present an overview of the camera design and readout and describe the current status
of the instrument and some results from the highly successful May/June 2010 observing run at the CSO with the
prototype camera, which verified the performance of the complete system (optics, antennas/filters, resonators,
and readout) and produced the first simultaneous 3-color observations with any MKID camera.
MUSIC (Multicolor Submillimeter kinetic Inductance Camera) is a new facility instrument for the Caltech Submillimeter
Observatory (Mauna Kea, Hawaii) developed as a collaborative effect of Caltech, JPL, the University
of Colorado at Boulder and UC Santa Barbara, and is due for initial commissioning in early 2011. MUSIC utilizes
a new class of superconducting photon detectors known as microwave kinetic inductance detectors (MKIDs), an
emergent technology that offers considerable advantages over current types of detectors for submillimeter and
millimeter direct detection. MUSIC will operate a focal plane of 576 spatial pixels, where each pixel is a slot line
antenna coupled to multiple detectors through on-chip, lumped-element filters, allowing simultaneously imaging
in four bands at 0.86, 1.02, 1.33 and 2.00 mm.
The MUSIC instrument is designed for closed-cycle operation, combining a pulse tube cooler with a two-stage
Helium-3 adsorption refrigerator, providing a focal plane temperature of 0.25 K with intermediate temperature
stages at approximately 50, 4 and 0.4 K for buffering heat loads and heat sinking of optical filters. Detector
readout is achieved using semi-rigid coaxial cables from room temperature to the focal plane, with cryogenic
HEMT amplifiers operating at 4 K. Several hundred detectors may be multiplexed in frequency space through
one signal line and amplifier.
This paper discusses the design of the instrument cryogenic hardware, including a number of features unique to
the implementation of superconducting detectors. Predicted performance data for the instrument system will
also be presented and discussed.
We present the results of the latest multicolor Microwave Kinetic Inductance Detector (MKID) focal plane arrays
in the submillimeter. The new detectors on the arrays are superconducting resonators which combine a coplanar
waveguide section with an interdigitated capacitor, or IDC. To avoid out-of-band pickup by the capacitor, a
stepped-impedance filter is used to prevent radiation from reaching the absorptive aluminum section of the
resonator. These arrays are tested in the preliminary demonstration instrument, DemoCam, a precursor to the
Multicolor Submillimeter Inductance Camera, MUSIC. We present laboratory results of the responsivity to light
both in the laboratory and at the Caltech Submillimeter Observatory. We assess the performance of the detectors
in filtering out-of-band radiation, and find the level of excess load and its effect on detector performance. We
also look at the array design characteristics, and the implications for the optimization of sensitivities expected
We report measurements of the fluctuations in atmospheric emission (atmospheric noise) above Mauna Kea
recorded with Bolocam at 143 GHz. These data were collected in November and December of 2003 with Bolocam
mounted on the Caltech Submillimeter Observatory (CSO), and span approximately 40 nights. Below ≃ 0.5 Hz,
the data time-streams are dominated by the f-δ atmospheric noise in all observing conditions. We were able to
successfully model the atmospheric fluctuations using a Kolmogorov-Taylor turbulence model for a thin wind-driven
screen in approximately half of our data. Based on this modeling, we developed several algorithms to
remove the atmospheric noise, and the best results were achieved when we described the fluctuations using a
low-order polynomial in detector position over the 8 arcminute focal plane. However, even with these algorithms,
we were not able to reach photon-background-limited instrument photometer (BLIP) performance at frequencies
below ≃ 0.5 Hz in any observing conditions. Therefore, we conclude that BLIP performance is not possible from
the CSO below ≃ 0.5 Hz for broadband 150 GHz receivers with subtraction of a spatial atmospheric template
on scales of several arcminutes.
The MKID Camera is a millimeter/submillimeter instrument being built for astronomical observations from the Caltech
Submillimeter Observatory. It utilizes microwave kinetic inductance detectors, which are rapidly achieving near-BLIP
sensitivity for ground-based observations, and a software-defined radio readout technique for elegant multiplexing of a
large number of detectors. The Camera will have 592 pixels distributed over 16 tiles in the focal plane, with four colors
per pixel matched to the 750 μm, 850 μm, and 1.0 - 1.5 mm (split in two) atmospheric transmission windows. As a
precursor to building the full-up camera and to enable ongoing detector testing, we have built a DemoCam comprised of
a 16-pixel MKID array with which we have made preliminary astronomical observations. These observations
demonstrate the viability of MKIDs for submillimeter astronomy, provide insight into systematic design issues that must
be considered for MKID-based instruments, and they are the first astronomical observations with antenna-coupled
superconducting detectors. In this paper, we describe the basic systems and specifications of the MKID Camera, we
describe our DemoCam observations, and we comment on the status of submillimeter MKID sensitivities.
Bolocam is a millimetre-wave (1.1 and 2.1 mm) camera with an array of 119 bolometers. It has been commissioned at the Caltech Submillimeter Observatory in Hawaii and is now in routine operation. Here we give an overview of the instrument and the data reduction pipeline. We discuss models of the sensitivity of Bolocam in different observing modes and under different atmospheric conditions. We briefly discuss observations of star-forming Galactic molecular clouds, a blank field survey for sub-millimeter galaxies, preliminary results of a blank-field CMB secondary anisotropy survey and discuss observations of galaxy clusters using the Sunyaev-Zel'dovich effect.