100 research outputs found
Calibration System with Cryogenically-Cooled Loads for CMB Polarization Detectors
We present a novel system to calibrate millimeter-wave polarimeters for CMB
polarization measurements. This technique is an extension of the conventional
metal mirror rotation approach, however it employs cryogenically-cooled
blackbody absorbers. The primary advantage of this system is that it can
generate a slightly polarized signal ( mK) in the laboratory; this is
at a similar level to that measured by ground-based CMB polarization
experiments observing a 10 K sky. It is important to reproduce the
observing condition in the laboratry for reliable characterization of
polarimeters before deployment. In this paper, we present the design and
principle of the system, and demonstrate its use with a coherent-type
polarimeter used for an actual CMB polarization experiment. This technique can
also be applied to incoherent-type polarimeters and it is very promising for
the next-generation CMB polarization experiments.Comment: 7 pages, 9 figures Submitted to RS
Innovative Demodulation Scheme for Coherent Detectors in CMB Experiments
We propose an innovative demodulation scheme for coherent detectors used in
cosmic microwave background polarization experiments. Removal of non-white
noise, e.g., narrow-band noise, in detectors is one of the key requirements for
the experiments. A combination of modulation and demodulation is used to
extract polarization signals as well as to suppress such noise. Traditional
demodulation, which is based on the two- point numerical differentiation, works
as a first-order high pass filter for the noise. The proposed demodulation is
based on the three-point numerical differentiation. It works as a second-order
high pass filter. By using a real detector, we confirmed significant
improvements of suppression power for the narrow-band noise. We also found
improvement of the noise floor.Comment: 3 pages, 4 figure
A systematical veto by all monitor signals in a gravitational-wave detector
We present the current state of veto studies in TAMA300 by monitor signals of the interferometer and its environment. In GW data analysis, fake GW events may bury real GW events or worse upper limits on the event rate. Thus, fake-event rejection is an important issue. In general, we can reject these fake events by the monitor signals, since these fake events are induced due to detector instabilities. However, using all monitor signals for the fake-event rejection would increase the accidental rejection probability and dead time without improving veto efficiency, since all monitor signals do not have correlations to the detector instabilities. Here, we analyze coincidences between the main and selected monitor signals with the optimal parameters for the fake-event rejection. Then, coincident events are rejected as the fake events. For the signal selection and parameter optimization, we systematically investigate the correlations with the detector instabilities. As a result, we achieved 30–99% veto efficiency using ten selected monitor signals with the 3.2% accidental rejection probability and 0.2% dead time
RFSoC-based front-end electronics for pulse detection
Radiation measurement relies on pulse detection, which can be performed using
various configurations of high-speed analog-to-digital converters (ADCs) and
field-programmable gate arrays (FPGAs). For optimal power consumption, design
simplicity, system flexibility, and the availability of DSP slices, we consider
the Radio Frequency System-on-Chip (RFSoC) to be a more suitable option than
traditional setups. To this end, we have developed custom RFSoC-based
electronics and verified its feasibility. The ADCs on RFSoC exhibit a flat
frequency response of 1-125 MHz. The root-mean-square (RMS) noise level is 2.1
ADC without any digital signal processing. The digital signal processing
improves the RMS noise level to 0.8 ADC (input equivalent 40 Vrms). Baseline
correction via digital signal processing can effectively prevent
photomultiplier overshoot after a large pulse. Crosstalk between all channels
is less than -55 dB. The measured data transfer speed can support up to 32 kHz
trigger rates (corresponding to 750 Mbps). Overall, our RFSoC-based electronics
are highly suitable for pulse detection, and after some modifications, they
will be employed in the Kamioka Liquid Scintillator Anti-Neutrino Detector
(KamLAND).Comment: 14 pages, 13 figure
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