Ultrasensitive TES Bolometers for Space Based FIR Astronomy

We present results from the development of a background limited transition edge sensor (TES) bolometer for the wavelength band 30–60 μm. The bolometer consists of a Ti/Au superconducting thermometer and a Ta radiation absorber deposited on a 200μm×300μm200μm×300μm membrane of SixNySixNy suspended on long, narrow legs. This device is voltage biased and the current through the device is measured by a SQUID amplifier. The thermometer has transition temperature Tc = 108 mKTc = 108 mK and the device is operated from a 70 mK base plate. FIR radiation is coupled into a multimodc horn with entrance aperture of 450 μm, length 4.5 mm and exit aperture of 45 μm, which feeds a metal integrating cavity containing the detector. The radiation band is defined by a pair of lowpass and highpass mesh filters in front of the horn. Here we present measurements of optical noise equivalent power (NEP), optical efficiency, dynamic range and time constant. The results show that measured TES detectors are close to meeting the requirement of the “Band 3” of SAFARI FTS imaging instrument [1] on the SPICA mission [2]

Optical requirements and modelling of coupling devices for the SAFARI instrument on SPICA

The next generation of space missions targeting far-infrared bands will require large-format arrays of extremely low-noise detectors. The development of Transition Edge Sensors (TES) array technology seems to be a viable solution for future mm-wave to Far-Infrared (FIR) space applications where low noise and high sensitivity is required. In this paper we concentrate on a key element for a high sensitivity TES detector array, that of the optical coupling between the incoming electromagnetic field and the phonon system of the suspended membrane. An intermediate solution between free space coupling and a single moded horn is where over-moded light pipes are used to concentrate energy onto multi-moded absorbers. We present a comparison of modelling techniques to analyse the optical efficiency of such light pipes and their interaction with the front end optics and detector cavity

Predicted modulated differential rates for direct WIMP searches at low energy transfers

The differential event rate for direct detection of dark matter, both the time averaged and the modulated one due to the motion of the Earth, are discussed. The calculations focus on relatively light cold dark matter candidates (WIMP) and low energy transfers. It is shown that for sufficiently light WIMPs the extraction of relatively large nucleon cross sections is possible. Furthermore for some WIMP masses the modulation amplitude may change sign, meaning that, in such a case, the maximum rate may occur six months later than naively expected. This effect can be exploited to yield information about the mass of the dark matter candidate, if and when the observation of the modulation of the event rate is established.Comment: 16 pages, 22 figures; references adde

Measuring CMB Polarization with BOOMERANG

BOOMERANG is a balloon-borne telescope designed for long duration (LDB) flights around Antarctica. The second LDB Flight of BOOMERANG took place in January 2003. The primary goal of this flight was to measure the polarization of the CMB. The receiver uses polarization sensitive bolometers at 145 GHz. Polarizing grids provide polarization sensitivity at 245 and 345 GHz. We describe the BOOMERANG telescope noting changes made for 2003 LDB flight, and discuss some of the issues involved in the measurement of polarization with bolometers. Lastly, we report on the 2003 flight and provide an estimate of the expected results.Comment: 12 pages, 8 figures, To be published in the proceedings of "The Cosmic Microwave Background and its Polarization", New Astronomy Reviews, (eds. S. Hanany and K.A. Olive). Fixed typos, and reformatted citation

Current constraints on Cosmological Parameters from Microwave Background Anisotropies

We compare the latest observations of Cosmic Microwave Background (CMB) Anisotropies with the theoretical predictions of the standard scenario of structure formation. Assuming a primordial power spectrum of adiabatic perturbations we found that the total energy density is constrained to be $\Omega_{tot}=1.03\pm0.06$ while the energy density in baryon and Cold Dark Matter (CDM) are $\Omega_bh^2=0.021\pm0.003$ and $\Omega_{cdm}h^2=0.12\pm0.02$, (all at 68% C.L.) respectively. The primordial spectrum is consistent with scale invariance, ($n_s=0.97\pm0.04$) and the age of the universe is $t_0=14.6\pm0.9$ Gyrs. Adding informations from Large Scale Structure and Supernovae, we found a strong evidence for a cosmological constant $\Omega_{\Lambda}=0.70_{-0.05}^{+0.07}$ and a value of the Hubble parameter $h=0.69\pm0.07$. Restricting this combined analysis to flat universes, we put constraints on possible 'extensions' of the standard scenario. A gravity waves contribution to the quadrupole anisotropy is limited to be $r \le 0.42$ (95% c.l.). A constant equation of state for the dark energy component is bound to be $w_Q \le -0.74$ (95% c.l.). We constrain the effective relativistic degrees of freedom $N_\nu \leq 6.2$ and the neutrino chemical potential $-0.01 \leq \xi_e \leq 0.18$ and $|\xi_{\mu,\tau}|\leq 2.3$ (massless neutrinos).Comment: The status of cosmological parameters before WMAP. In press on Phys. Rev. D., Rapid Communication, 6 pages, 5 figure

Evidence against or for topological defects in the BOOMERanG data ?

The recently released BOOMERanG data was taken as ``contradicting topological defect predictions''. We show that such a statement is partly misleading. Indeed, the presence of a series of acoustic peaks is perfectly compatible with a non-negligible topological defects contribution. In such a mixed perturbation model (inflation and topological defects) for the source of primordial fluctuations, the natural prediction is a slightly lower amplitude for the Doppler peaks, a feature shared by many other purely inflationary models. Thus, for the moment, it seems difficult to rule out these models with the current data.Comment: 4 pages, 1 figure. Some changes following extraordinarily slow referee Reports and new data. Main results unchanged (sorry

The BOOMERanG experiment and the curvature of the Universe

We describe the BOOMERanG experiment and its main result, i.e. the measurement of the large scale curvature of the Universe. BOOMERanG is a balloon-borne microwave telescope with sensitive cryogenic detectors. BOOMERanG has measured the angular distribution of the Cosmic Microwave Background on $\sim 3$ of the sky, with a resolution of $\sim 10$ arcmin and a sensitivity of $\sim 20 \mu K$ per pixel. The resulting image is dominated by hot and cold spots with rms fluctuations $\sim 80 \mu K$ and typical size of $\sim 1^o$. The detailed angular power spectrum of the image features three peaks and two dips at $\ell = (213^{+10}_{-13}), (541^{+20}_{-32}), (845^{+12}_{-25})$ and $\ell = (416^{+22}_{-12}), (750^{+20}_{-750})$, respectively. Such very characteristic spectrum can be explained assuming that the detected structures are the result of acoustic oscillations in the primeval plasma. In this framework, the measured pattern constrains the density parameter $\Omega$ to be $0.85 < \Omega < 1.1$ (95% confidence interval). Other cosmological parameters, like the spectral index of initial density fluctuations, the density parameter for baryons, dark matter and dark energy, are detected or constrained by the BOOMERanG measurements and by other recent CMB anisotropy experiments. When combined with other cosmological observations, these results depict a new, consistent, cosmological scenario.Comment: Proc. of the Erice School on "Neutrinos in Astro, Particle and Nuclear Physics", 18.-26. September 2001, Amand Faessler, Jan Kuckei eds, "Progress in Particle and Nuclear Physics", vol. 4

The Einstein polarization interferometer for cosmology (EPIC) and the millimeter-wave bolometric interferometer (MBI)

We provide an overview of a mission concept study underway for the Einstein Inflation Probe (EIP). Our study investigates the advantages and tradeoffs of using an interferometer (EPIC) for the mission. We also report on the status of the millimeter-wave bolometric interferometer (MBI), a ground-based pathfinder optimized for degree-scale CMB polarization measurements at 90 GHz

Special Libraries, April 1933

Volume 24, Issue 3https://scholarworks.sjsu.edu/sla_sl_1933/1002/thumbnail.jp

A Determination of the Hubble Constant Using Measurements of X-Ray Emission and the Sunyaev-Zeldovich Effect at Millimeter Wavelengths in the Cluster Abell 1835

We present a determination of the Hubble constant and central electron density in the cluster Abell 1835 (z = 0.2523) from measurements of X-ray emission and millimeter-wave observations of the Sunyaev-Zeldovich (S-Z) effect with the Sunyaev-Zeldovich Infrared Experiment (SuZIE) multifrequency array receiver. Abell 1835 is a well studied cluster in the X-ray with a large central cooling flow. Using a combination of data from ROSAT PSPC and HRI images and millimeter wave measurements we fit a King model to the emission from the ionized gas around Abell 1835 with θ0 = 022 ± 002 and β = 0.58 ± 0.02. Assuming the cluster gas to be isothermal with a temperature of 9.8 keV, we find a y-parameter of 4.9 ± 0.6 × 10-4 and a peculiar velocity of 500 ± 1000 km s-1 from measurements at three frequencies, 145, 221, and 279 GHz. Combining the S-Z measurements with X-ray data, we determine a value for the Hubble constant of H0 = 59 km s-1 Mpc-1 and a central electron density for Abell 1835 of ne0 = 5.64 × 10-2 cm-3 assuming a standard cosmology with Ωm = 1 and ΩΛ = 0. The error in the determination of the Hubble constant is dominated by the uncertainty in the temperature of the X-ray emitting cluster gas