Resonant-mass Gravitational Wave Detector Research Articles

Ultra-stable optical clock cavities as resonant mass gravitational wave detectors in search for new physics

We propose using table-top-size ultra-stable optical cavities from state-of-the-art optical atomic clocks as bar gravitational wave detectors for frequencies higher than 2 kHz. We show that the 2-20 kHz range of gravitational waves' spectrum can be accessed with instruments below 2 meters in size. The materials and properties of the proposed cavities are in the grasp of today's technology. The ultra-stable optical cavities allow detection not only predicted gravitational wave signals from such sources as binary neutron star mergers and post-mergers, subsolar-mass primordial black-hole mergers, and collapsing stellar cores, but can also reach new physics beyond the standard model, looking for ultralight bosons such as QCD axions and axion-like particles formed through black hole superradiance.

The laser interferometric gravitational wave detector calibrator suspension: First attempt

AbstractIn 2015 the first detection of gravitational waves (GW) was made; such detection was made by kilometer size interferometer detectors. The calibration of such a detector is still a challenge then a calibrator was proposed. This calibrator is a resonant mass gravitational wave detector that operates at frequencies where the GW have been detected. This work shows part of the challenges of making a suspension for this device. The device has its vibration mode simulated in Finite Element Methods, then the parts of the device which have less movement were chosen to connect the suspension. Other simulations were made with the complete system and the results were analyzed.

Modelling a mechanical antenna for a calibrator for interferometric gravitational wave detector using finite elements method

Interferometric gravitational wave detectors (IGWD) are a very complex detector, the need to lock the detector in a dark fringe condition besides the vibrations that affect the mirrors, creates the necessity of using active suspension systems. These active systems make the system reach the desired sensitivity but make the calibration of such detectors much more difficult. To solve this problem a calibrator is proposed, a resonant mass gravitational wave detector could be used to detect the same signal in a narrower band and use the measured amplitude to calibrate the IGWD, as resonant mass gravitational wave detectors are easily calibrated. This work aims to design the mechanical antenna of such a calibrator. The main difficulty is to design the calibrator is the frequencies required to make the detection. These massive detectors usually were made in frequencies close to 1 kHz and the frequency range to operate for better sensitivity is around 100 Hz. The antenna is modelled in finite elements method and a design of such an antenna is presented.

Obtaining the sensitivity of a calibrator for interferometric gravitational wave

Interferometric gravitational wave detectors (IGWD) are a very complex detector, the need to lock the detector in a dark fringe condition besides the vibrations that affect the mirrors, creates the necessity of using active suspension systems. These active systems make the system reach the desired sensitivity but make the calibration of such detectors much more difficult. To solve this problem a calibrator is proposed, a resonant mass gravitational wave detector could be used to detect the same signal in a narrower band and use the measured amplitude to calibrate the IGWD, as resonant mass gravitational wave detectors are easily calibrated. This work aims to obtain the expected sensitivity of such a calibrator by using lumped modelling in such mechanical detectors. The calibrator is modelled as a spring mass system and the sensitivity curve is presented calculated in by a matlab program. The curve shows that using state of art parameters for the detector the final sensitivity is close to the quantum limit and can be used to calibrate the IGWDs.

Obtaining the frequencies of Schenberg detector sphere using finite element modelling

The resonant-mass gravitational wave detector SCHENBERG is a spherical detector that operates with a central frequency close to 3200 Hz and a bandwidth around 200 Hz. It has a spherical mass that works as an antenna whose weight is 1150 kg and is connected to the outer environment by a suspension system designed to attenuate local noise due to seism as well as other sources; the sphere is suspended by its center of mass. When a gravitational wave passes by the detector, the antenna is expected to vibrate. This motion should be monitored by six parametric microwave transducers whose output signals will be digitally analyzed. In order to determine the detector performance better, it is necessary to obtain the vibration frequencies of the sphere with a better precision. To achieve such a goal the sphere with the holes to mount the transducers and the central hole from which the sphere is suspended is simulated in a finite element method program when the gravity is applied to the sphere and the deformation is kept. After that the vibration normal modes of the sphere are calculated and they are compared to the experimental results.

Prototype superfluid gravitational wave detector

We study a cross-shaped cavity filled with superfluid $^4$He as a prototype resonant-mass gravitational wave detector. Using a membrane and a re-entrant microwave cavity as a sensitive optomechanical transducer, we were able to observe the thermally excited high-$Q$ acoustic modes of the helium at 20 mK temperature and achieved a strain sensitivity of $8 \times 10^{-19}$ Hz$^{-1/2}$ to gravitational waves. To facilitate the broadband detection of continuous gravitational waves, we tune the kilohertz-scale mechanical resonance frequencies up to 173 Hz/bar by pressurizing the helium. With reasonable improvements, this architecture will enable the search for GWs in the 1-30 kHz range, relevant for a number of astrophysical sources both within and beyond the Standard Model.

On the Dilution Refrigerator Thermal Connection for the SCHENBERG Gravitational Wave Detector

The resonant-mass gravitational wave detector SCHENBERG was designed by the Brazilian group Graviton to be sensitive to a central frequency nearing 3200 Hz and a bandwidth of 200 Hz. It has a spherical antenna weighing 1150 kg that is connected to the outer environment by a suspension system designed to attenuate local noise due to seism as well as other sources. Should a gravitational wave pass by the detector, the antenna is expected to vibrate. This motion will be monitored by six parametric transducers whose output signals will be digitally analyzed. In order to improve the sensitivity of the detector, it must be cooled down to the lowest possible temperature, and for this purpose a dilution refrigerator is planned to be implemented in the detector. It is known that such device produces vibration when operational, consequently introducing noise in the system. Using the finite elements method, this work investigates thermal connections between the dilution refrigerator and the sphere suspension that allow the detector to operate within its projected sensitivity. The finite elements method showed an attenuation of 240dB in the best-valued thermal connection.

The Surface Treatment of Niobium Superconducting Reentrant Cavities by Means of High Temperature Nitrogen Plasma Based Ion Implantation

High Temperature Nitrogen Plasma Based Ion Implantation (HT-NPBII) has been used to treat the surface of niobium superconducting reentrant cavities, which are part of parametric transducers in a resonant-mass gravitational wave detector. The aim is to enhance the corresponding electrical quality factors (Q-factors) which are closely related with the increase of the sensitivity of the system. In this experiment, the cavities are immersed in plasma and bombarded by energetic nitrogen ions, which are implanted into the surfaces of these heated substrates. The heating temperature of the cavities is controlled during the treatment and its level directly affects the N implantation depth profile due to the diffusion process. Additional tailoring of the nitrogen doping can be performed by the adjustment of the intensity and the duty cycle of the high negative voltage pulses used for ion implantation. For implantations performed at 5 kV /20 µs /300 Hz/ 700 °C, nitrogen atoms occupy interstitial spaces in the crystal lattice of niobium. The treatment of niobium superconducting cavities under these parameters caused the enhancement of two orders of magnitude of respective Q-factors. A set of characterization techniques was performed herein in order to help with the understanding of the underlying mechanism behind this phenomenon.

On the Cabling Seismic Isolation for the Microwave Transducers of the Schenberg Detector

Schenberg is a resonant-mass gravitational wave detector developed by the Brazilian Graviton group that is sensitive to a central frequency near 3200 Hz with bandwidth around 200 Hz. Its spherical antenna weighs 1150 kg and it is connected to the outer environment by a suspension system designed to attenuate local noise, both seismic and non-seismic. During the passage of a gravitational wave the antenna is expected to vibrate and such motion will be monitored by six parametric transducers whose electronic signal will be digitally analyzed. For the microwaves to reach the transducers, coaxial cables are needed, which are also connected to the outer environment and may be a source of seismic noise. Using the finite elements method, this work shows that the proper addition of masses along these cables reduces such seismic noise to levels below the detector’s thermal noise when it operates at 50 mK, thus avoiding the decrease of the expected sensitivity of the detector.

4a-D-6 光共振器を用いた共振型重力波検出器用トランスデューサーの開発(III)

4a-D-6 光共振器を用いた共振型重力波検出器用トランスデューサーの開発(III)

Schenberg microwave cabling seismic isolation.

SCHENBERG is a resonant-mass gravitational wave detector with a frequency about 3.2 kHz. Its spherical antenna, weighing 1.15 metric ton, is connected to the external world by a system which must attenuate seismic noise. When a gravitational wave passes the antenna vibrates, its motion is monitored by transducers. These parametric transducers uses microwaves carried by coaxial cables that are also connected to the external world, they also carry seismic noise. In this analysis the system was modeled using finite element method. This work shows that the addition of masses along these cables can decrease this noise, so that this noise is below the thermal noise of the detector when operating at 50 mK.

Study of the effect of NbN on microwave Niobium cavities for gravitational wave detectors

Superconducting reentrant cavities may be used in parametric transducers for resonant-mass gravitational wave detectors. When coupled to a spherical resonant antenna, transducers will monitor its mechanical quadrupolar modes, working as a mass-spring system. In this paper we will investigate the effect of the Niobium Nitride (NbN), produced through plasma immersion ion implantation (PIII), on the quality factor of reentrant Niobium (Nb) cavities. With the PIII surface treatment unloaded electrical Q-factors (Q0) of the order of 105 were obtained in cryogenic conditions. These results indicated a significant increase in the effect of superconductivity after the cavity surfaces have been heavily attacked by a concentrated acid mixture and after suffering successive PIII processes. Q0's ∼ 3.0 × 105 at 4.2 K are expected to be obtained using Nb RRR399 with a suitable surface treatment. These cavities, with high Q0, are already installed and being tested in the Gravitational Wave Detector Mario Schenberg. The experimental tests have been carried out at the laboratories of the National Institute for Space Research (INPE).

On the Massive Antenna Suspension System in the Brazilian Gravitational Wave Detector SCHENBERG

SCHENBERG is a resonant-mass gravitational wave detector built in Brazil. Its spherical antenna, weighting 1.15 t, is connected to the outside world by a suspension system whose main function is to attenuate the external seismic noise. In this work, we report how the system was modeled using finite elements method. The model was validated on experimental data. The simulation showed that the attenuation obtained is of the order of 260 dB, which is sufficient for decreasing the seismic noise below the level of the thermal noise of the detector operating at 50 mK.

High sensitivity niobium parametric transducer for the Mario Schenberg gravitational wave detector

Parametric transducers can work below the quantum limit of sensitivity for resonant mass gravitational wave detectors. This makes them a promising alternative for electromechanical transductance for such detectors. These transducers consist of a reentrant superconducting niobium cavity coupled to a mass-spring system with three mechanical modes. These cavities have a central post responsible for creating a narrow axial gap between its top and the cavity wall, which is a resonant membrane. Their displacement sensitivity (df/dx) increases as the gap spacing decreases. However, this is not a linear relationship and the dimensioning of the cavity becomes critical if the gap is of the order of a few microns. In this paper, we describe how to obtain a gap spacing of ∼ 3 μ m and also the development of parametric transducers that will be employed in the coming experimental runs of the Schenberg gravitational wave antenna. Mechanical thinning methods were performed followed by mechanical and electrical frequency measurements to tune the device to operate at the required frequencies. The main results present better frequency stability and an improvement of df/dx by one order of magnitude higher than the preceding models. These results will allow us to reach the quantum limit of detector sensitivity of ∼ 10−22 Hz−1/2 in the near future, making it possible to search for gravitational waves around 3.2 kHz.

Past, present and future of the Resonant-Mass gravitational wave detectors

Resonant-mass gravitational wave detectors are reviewed from the concept of gravitational waves and its mathematical derivation, using Einstein's general relativity, to the present status of bars and spherical detectors, and their prospects for the future, which include dual detectors and spheres with non-resonant transducers. The review not only covers technical aspects of detectors and sciences that will be done, but also analyzes the subject in a historical perspective, covering the various detection efforts over four decades, starting from Weber's pioneering work.

Investigation of ultra-high sensitivity klystron cavity transducers for broadband resonant-mass gravitational wave detectors

Since the Stanford pioneering work of Paik in the 1970s, cryogenic resonant-mass gravitational wave detectors have used resonant transducers, which have the effect of increasing both the detector sensitivity and bandwidth. Now nanotechnology is opening new possibilities towards the construction of ultra-high sensitivity klystron cavity transducers. It might be feasible to construct TeraHz/micron parametric transducers in a near future. They would be so sensitive that there would be no need for multimode resonant transducers. The resonant-antenna would act as a broadband detector for gravitational waves. A spherical antenna, such as Schenberg or Mini-Grail, could add to this quality the advantage of wave position and polarity determination. Here we propose an extreme geometry for a re-entrant klystron cavity (df/dg ∼ 1018 Hz/m, where f stands for the microwave pump frequency and g for variations in the cavity gap), obtaining a frequency response for the strain sensitivity of the Schenberg gravitational wave detector such that its bandwidth increases from 50 Hz (using the so-called resonant mode coupling) to ∼4000 Hz when operating @ 20 mK, and, when compared to LIGO experimental curve, shows a competitive band of about 2000 Hz. We also study some of the technological complications that can be foreseen to design such a resonant cavity.

SQUID Developments for the Gravitational Wave Antenna MiniGRAIL

We designed two different sensor SQUIDs for the readout of the resonant mass gravitational wave detector MiniGRAIL. Both designs have integrated input inductors in the order of 1.5 muH and are planned for operation in the mK temperature range. Cooling fins were added to the shunt resistors. The fabricated SQUIDs show a behavior that differs from standard DC-SQUIDs. We were able to operate a design with a parallel configuration of washers at reasonable sensitivities. The flux noise saturated to a value of 0.84 muPhi0/radicHz below a temperature of 200 mK. The equivalent noise referred to the current through the input coil is 155 fA/radicHz and the energy resolution yields 62 h.

Studying a new shape for mechanical impedance matchers in Mario Schenberg transducers

``Mario Schenberg'' is a spherical resonant-mass gravitational wave (GW) detector that is expected to be part of a GW detection array of two detectors. Another one is been built in The Netherlands. Their resonant frequencies will be around 3 kHz with a bandwidth of about 200 Hz. This range of frequencies is new in a field where the typical frequencies lay below 1 kHz, making the transducer development much more complex. Some studies indicated that the use of low mass mechanical resonators (used for impedance matching to the parametric transducer, in a cold damping regime) allows the detector to reach the standard quantum limit. In this work we describe the study of a new shape for the impedance matching resonator used to obtain a better coupling between the sphere and the transducers and a better use of the space inside the experimental chamber.

Planning to improve the mechanical quality factor in the transducer impedance matchers for Mario Schenberg detector

"Mario Schenberg" is a spherical resonant-mass gravitational wave (GW) detector that will be part of a GW detection array of two detectors. Another one is been built in The Netherlands. Their resonant frequencies will be around 3.2 kHz with a bandwidth of about 200 Hz. This range of frequencies is new in a field where the typical frequencies lay below 1 kHz, making the transducer development much more complex. Some studies indicated that using low mass mechanical resonators (used for impedance matching to the parametric transducer, in a cold damping regime) allow the detector to reach the standard quantum limit. In this work we describe the procedures that are being developed to quickly test the mechanical quality factor of a very small resonator in the quest to find the best machining method and thermal annealing for the impedance matching resonator, one key part that makes a good coupling between the sphere and the transducer. The main goal is to optimize the mechanical quality factor in a reasonable time.

Challenges in signal analysis of resonant-mass gravitational wave detectors

An overview of the main points related to data analysis in resonant-mass gravitational wave detectors will be presented. Recent developments on the data analysis system for the Brazilian detector SCHENBERG will be emphasized.