The status of the QUIJOTE multi-frequency instrument

Abstract

The QUIJOTE-CMB project has been described in previous publications. Here we present the current status of the QUIJOTE multi-frequency instrument (MFI) with five separate polarimeters (providing 5 independent sky pixels): two which operate at 10-14 GHz, two which operate at 16-20 GHz, and a central polarimeter at 30 GHz. The optical arrangement includes 5 conical corrugated feedhorns staring into a dual reflector crossed-draconian system, which provides optimal cross-polarization properties (designed to be < −35 dB) and symmetric beams. Each horn feeds a novel cryogenic on-axis rotating polar modulator which can rotate at a speed of up to 1 Hz. The science driver for this first instrument is the characterization of the galactic emission. The polarimeters use the polar modulator to derive linear polar parameters Q, U and I and switch out various systematics. The detection system provides optimum sensitivity through 2 correlated and 2 total power channels. The system is calibrated using bright polarized celestial sources and through a secondary calibration source and antenna. The acquisition system, telescope control and housekeeping are all linked through a real-time gigabit Ethernet network. All communication, power and helium gas are passed through a central rotary joint. The time stamp is synchronized to a GPS time signal. The acquisition software is based on PLCs written in Beckhoffs TwinCat and ethercat. The user interface is written in LABVIEW. The status of the QUIJOTE MFI will be presented including pre-commissioning results and laboratory testing.

QUIJOTE-CMB experiment: a technical overview

“…The instrument was initially designed with five chains of polarimeters although the central one, corresponding to the frequency of 30 GHz, had to be removed and also a more powerful cool-head was used in order to increase the cooling power of the cryostat and in this way assure the temperature range needed inside the can. The original MFI five chains design is described in reference [4].…”

A High-Sensitivity Fourier Transform Spectrometer for Cosmic Microwave Background Observations

“…[1], [2], [3], [4]). The present plan is to extend the goals of the QUIJOTE-CMB Experiment ( [5], [6], [7], [8]) by building a new microwave spectrometer in the frequency range [10][11][12][13][14][15][16][17][18][19][20] GHz. The measurement of the CMB spectrum to the accuracy that will reveal interesting science is particularly difficult because there are many uncertainties that lead to effects of the order of this level.…”

“…On the other hand, a broad instantaneous bandwidth of 10-20 GHz allows an increase of the sensitivity by a factor √ ∆ν at the cost of loosing spectral resolution if this were necessary. Since the entire band of the experiment is measured simultaneously, the TMS relative calibration between bands is expected to be more stable and presents lower uncertainty than the other experiment taking CMB measurements in the same frequency band in the north hemisphere, the Multi Frequency Instrument (MFI) [19], which presents four bands centered at 11, 13, 17 and 19 GHz with 2 GHz bandwidth, so the higher resolution of the TMS in comparison with the MFI will provide important information on narrow band interferences and features such as ozone.…”

“…Abstract-The QUIJOTE Experiment was developed to study the polarization in the Cosmic Microwave Background (CMB) over the frequency range of 10-50 GHz. Its first instrument, the Multi Frequency Instrument (MFI), measures in the range [10][11][12][13][14][15][16][17][18][19][20] GHz which coincides with one of the naturally transparent windows in the atmosphere. The Tenerife Microwave Spectrometer (TMS) has been designed to investigate the spectrum between 10-20 GHz in more detail.…”

Octave bandwidth hybrid-coupled microstrip diplexer for a broadband radio astronomy receiver

“…Moreover, the 10-20 GHz receiver will also complement the measurements and data of the multifrequency instrument of the QUIJOTE project operating in the same frequency band but in a different topology. 6 Therefore, in this receiver from 10 to 20 GHz, an electro-optical a) Author to whom correspondence should be addressed: villae@unican.es interferometer is proposed to complement the latter data, and it is composed of two separate frequency bands (10-14 GHz and 16-20 GHz) to properly perform the microwave to optical frequency conversion.…”