Arlette de Waard

Insertable system for fast turnaround time microwave experiments in a dilution refrigerator

Microwave experiments in dilution refrigerators are a central tool in the field of superconducting quantum circuits and other research areas. This type of experiments relied so far on attaching a device to the mixing chamber of a dilution refrigerator. The minimum turnaround time in this case is a few days as required by cooling down and warming up the entire refrigerator. We developed a new approach, in which a suitable sample holder is attached to a cold-insertable probe and brought in contact with transmission lines permanently mounted inside the cryostat. The total turnaround time is 8 h if the target temperature is 80 mK. The lowest attainable temperature is 30 mK. Our system can accommodate up to six transmission lines, with a measurement bandwidth tested from zero frequency to 12 GHz. This bandwidth is limited by low-pass components in the setup; we expect the intrinsic bandwidth to be at least 18 GHz. We present our setup, discuss the experimental procedure, and give examples of experiments enabled by this system. This new measurement method will have a major impact on systematic ultra-low temperature studies using microwave signals, including those requiring quantum coherence.

The Cryostat of the CUORE Project, a 1-ton Scale Cryogenic Experiment for Neutrinoless Double Beta Decay Research

CUORE is a new generation of 1-ton scale cryogenic detector for rare-events physics. CUORE, a detector to search Neutrinoless Double Beta Decay of 130Te, is an array of 988 TeO2 crystals of a mass of 750 g each. To build the cryogenic system, where the CUORE detector will be installed in the Gran Sasso Underground Laboratory, is really a challenge. It is a large cryogen-free cryostat cooled by pulse tubes and by a high power dilution refrigerator. To avoid radioactive background, about 10000 kg of lead will be cooled to below 1 K and only few construction materials are acceptable. the detector will have a total mass of about 1500 kg and must be cooled to less than 10 mK in a vibration-free environment.

Development of a SQUID readout system for the MiniGRAIL

The MiniGRAIL is one of the three similar spherical gravitational wave detectors that are currently being developed. The detector has a resonant frequency of about 3 kHz and will be operated at 20 mK. The ultimate goal is to use a readout system consisting of six transducers coupled to nearly quantum limited two-stage SQUIDs. The two-stage SQUIDs are based on double relaxation oscillation SQUIDs, which enables a direct voltage readout scheme. We have developed nonintegrated two-stage SQUIDs and experimentally verified the proper operation of the system coupled to a capacitive transducer. Based on the results that were achieved, integrated two-stage SQUIDs were designed. Special attention has been paid to the sensor SQUID, the back action of the SQUID and the feedback scheme that is used for linearizing the SQUID output.

MiniGRAIL, A 65 cm spherical antenna

We intend to build a 65 cm diameter spherical, cryogenic gravitational wave antenna made of the CuAl(6%) alloy with a mass of 1168 Kg, a resonance frequency of 3.7 kHz and a bandwidth around 300 Hz. The quantum-limited strain sensitivity δL/L would be 2.2×10−21 at 10 mK. We believe that a sensitivity around 5×10−20 could be reached within the duration of the project, which is (at that frequency) comparable to that of the large interferometers LIGO and VIRGO presently being built. The sources we are aiming at are for instance non-axisymmetric dynamical instabilities of rotating neutron stars within our galaxy, where 108 neutron stars are expected to exist.

Acoustic resonance widening in GW detectors: detailed modelling of the dissipation processes

Internal friction effects are responsible for line widening of the acoustic resonance frequencies in mechanical oscillators and result in damped oscillations of its eigenmodes with a decay time Q/ω. We study the solutions to the equations of motion for the case of spherical oscillators, to be used as the next generation of acoustic gravitational wave detectors, based on various different assumptions about the materials constituent equations. Quality factor dependence on mode frequency is determined in each case, and a discussion of its applicability to actual gravitational wave detectors is made on the basis of available experimental evidence.