Publications (5)0 Total impact
ABSTRACT: 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, lumped-element on-chip bandpass filters to
define spectral bands, and microwave kinetic inductance detectors to
senseincoming 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-of-band
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.
ABSTRACT: Submillimeter cameras now have up to $10^4$ pixels (SCUBA 2). The proposed
CCAT 25-meter submillimeter telescope will feature a 1 degree field-of-view.
Populating the focal plane at 350 microns would require more than $10^6$
photon-noise limited pixels. To ultimately achieve this scaling, simple
detectors and high-density multiplexing are essential. We are addressing this
long-term challenge through the development of frequency-multiplexed
superconducting microresonator detector arrays. These arrays use
lumped-element, direct-absorption resonators patterned from titanium nitride
films. We will discuss our progress toward constructing a scalable 350 micron
pathfinder instrument focusing on fabrication simplicity, multiplexing density,
and ultimately a low per-pixel cost.
ABSTRACT: 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.
ABSTRACT: 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. The entire system is open sourced, and can be customized to meet challenging requirement in many applications: e.g. MKID, MSQUID etc.