A New Cryogenic Apparatus to Search for the Neutron Electric Dipole Moment
M. W. Ahmed, R. Alarcon, A. Aleksandrova, S. Baessler, L. Barron-Palos, L. M. Bartoszek, D. H. Beck, M. Behzadipour, I. Berkutov, J. Bessuille, M. Blatnik, M. B… 展开作者
M. W. Ahmed, R. Alarcon, A. Aleksandrova, S. Baessler, L. Barron-Palos, L. M. Bartoszek, D. H. Beck, M. Behzadipour, I. Berkutov, J. Bessuille, M. Blatnik, M. Broering, L. J. Broussard, M. Busch, R. Carr, V. Cianciolo, S. M. Clayton, M. D. Cooper, C. Crawford, S. A. Currie, C. Daurer, R. Dipert, K. Dow, D. Dutta, Y. Efremenko, C. B. Erickson, B. W. Filippone, N. Fomin, H. Gao, R. Golub, C. R. Gould, G. Greene, D. G. Haase, D. Hasell, A. I. Hawari, M. E. Hayden, A. Holley, R. J. Holt, P. R. Huffman, E. Ihloff, S. K. Imam, T. M. Ito, M. Karcz, J. Kelsey, D. P. Kendellen, Y. J. Kim, E. Korobkina, W. Korsch, S. K. Lamoreaux, J. Leggett, K. K. H. Leung, A. Lipman, C. Y. Liu, J. Long, S. W. T. MacDonald, M. Makela, A. Matlashov, J. D. Maxwell, M. Mendenhall, H. O. Meyer, R. G. Milner, P. E. Mueller, N. Nouri, C. M. O'Shaughnessy, C. Osthelder, J. C. Peng, S. I. Penttila, N. S. Phan, B. Plaster, J. C. Ramsey, T. M. Rao, R. P. Redwine, A. Reid, A. Saftah, G. M. Seidel, I. Silvera, S. Slutsky, E. Smith, W. M. Snow, W. Sondheim, S. Sosothikul, T. D. S. Stanislaus, X. Sun, C. M. Swank, Z. Tang, R. Tavakoli Dinani, E. Tsentalovich, C. Vidal, W. Wei, C. R. White, S. E. Williamson, L. Yang, W. Yao, A. R. Young
A cryogenic apparatus is described that enables a new experiment, nEDM@SNS, with a major improvement in sensitivity compared to the existing limit in the search for a neutron Electric Dipole Moment (EDM). It uses superfluid $^4$He to produce a high density of Ultra-Cold Neutrons (UCN) which are contained in a suitably coated pair of measurement cells. The experiment, to be operated at the Spallation Neutron Source at Oak Ridge National Laboratory, uses polarized $^3$He from an Atomic Beam Source injected into the superfluid $^4$He and transported to the measurement cells as a co-magnetometer. The superfluid $^4$He is also used as an insulating medium allowing significantly higher electric fields, compared to previous experiments, to be maintained across the measurement cells. These features provide an ultimate statistical uncertainty for the EDM of $2-3\times 10^{-28}$ e-cm, with anticipated systematic uncertainties below this level.
A magnetic coil operated at cryogenic temperatures is used to produce spatial, relative field gradients below 6 ppm/cm, stable for several hours. The apparatus is a prototype of the magnetic components for a neutron electric dipole moment (nEDM) search, which will take place at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory using ultra-cold neutrons (UCN). That search requires a uniform magnetic field to mitigate systematic effects and obtain long polarization lifetimes for neutron spin precession measurements. This paper details upgrades to a previously described apparat…
We report a homebuilt ultra-high-vacuum (UHV) rotating sample manipulator with cryogenic cooling. The sample holder is thermally anchored to a built-in cryogenic cold head through flexible copper beryllium strips, permitting continuous sample rotation. A similar contact mechanism is implemented for the electrical wiring to the sample holder for thermometry. The apparatus thus enables continuous sample rotation at regulated cryogenic temperatures in a UHV environment. We discuss the potential applications of this apparatus for cryogenic sputtering.
The Cryogenic Apparatus for Precision Tests of Argon Interactions with Neutrinos (CAPTAIN) is being built at Los Alamos National Laboratory. A hexagonal time projection chamber (TPC) with a 1 m drift length will be constructed inside a cryostat containing 7,700L of liquid argon. CAPTAIN will be used to test interactions using beams of neutrons and neutrinos. It will serve as a test bed for various options for the Long Baseline Neutrino Experiment (LBNE) including in the photon detection system. The current photon detection system will be described and future options discussed. The system is co…
We describe the design, commissioning and operation of an ultra-low-vibration closed-cycle cryogenic ion trap apparatus. One hundred lines for low-frequency signals and eight microwave / radio frequency coaxial feed lines offer the possibility of implementing a small-scale ion-trap quantum processor or simulator. With all supply cables attached, more than 1.3 W of cooling power at 5 K is still available for absorbing energy from electrical pulses introduced to control ions. The trap itself is isolated from vibrations induced by the cold head using a helium exchange gas interface. The performan…
A system providing an optical frequency with an instability comparable to that of a hydrogen maser is presented. It consists of a $5$ $\mathrm{cm}$ long, vertically oriented silicon optical resonator operated at temperatures between $1.5$ $\mathrm{K}$ and $3.6$ $\mathrm{K}$ in a closed-cycle cryostat with low-temperature Joule-Thomson stage. We show that with a standard cryostat, a simple cryogenic optomechanical setup, no active or passive vibration isolation, a minimum frequency instability of $2.5\times10^{-15}$ at $τ=1500$ $\mathrm{s}$ integration time can be reached. The influence of puls…
A cryogenic apparatus with a rotatable substrate for matrix isolation spectroscopy of BaF in neon crystals down to 3.2 K
Istituto Nazionale di Fisica Nucleare（意大利国家核物理研究所）；University of Ferrara（费拉拉大学）；University of Padua（帕多瓦大学）；National Quantum Science and Technology Institute（国家量子科学与技术研究所）
A description is presented of apparatus used to carry out an experimental search for an electric dipole moment of the neutron, at the Institut Laue-Langevin (ILL), Grenoble. The experiment incorporated a cohabiting atomic-mercury magnetometer in order to reduce spurious signals from magnetic field fluctuations. The result has been published in an earlier letter; here, the methods and equipment used are discussed in detail.
High voltage and electrode system for a cryogenic experiment to search for the neutron electric dipole moment
Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）；W. K. Kellogg Radiation Laboratory, California Institute of Technology（加州理工学院 W.K. 凯洛格辐射实验室）；Oak Ridge National Laboratory（橡树岭国家实验室）；Department of Physics, Brown University（布朗大学物理系）
A permanent electric dipole moment of fundamental spin-1/2 particles violates both parity (P) and time re- versal (T) symmetry, and hence, also charge-parity (CP) symmetry since there is no sign of CPT-violation. The search for a neutron electric dipole moment (nEDM) probes CP violation within and beyond the Stan- dard Model. The experiment, set up at the Paul Scherrer Institute (PSI), an improved, upgraded version of the apparatus which provided the current best experimental limit, dn < 2.9E-26 ecm (90% C.L.), by the RAL/Sussex/ILL collaboration: Baker et al., Phys. Rev. Lett. 97, 131801 (200…
We implemented a low noise current preamplifier for the readout of resistive bolometers. We tested the apparatus on thermometer resistances ranging from 10 Ohm to 500 Mohm. The use of current preamplifier overcomes constraints introduced by the readout time constant due to the thermometer resistance and the input capacitance. Using cold JFETs, this preamplifier board is shown to have very low noise: the Johnson noise of the source resistor (1 fA/Hz1/2) dominated in our noise measurements. We also implemented a lock-in chain using this preamplifier. Because of fast risetime, compensation of the…
A discovery of a permanent electric dipole moment (EDM) of the neutron would provide one of the most important low energy tests of the discrete symmetries beyond the Standard Model of particle physics. A new search of neutron EDM, to be conducted at the spallation neutron source (SNS) at ORNL, is designed to improve the present experimental limit of ~10^-26 e-cm by two orders of magnitude. The experiment is based on the magnetic-resonance technique in which polarized neutrons precess at the Larmor frequency when placed in a static magnetic field; a non-zero EDM would be evident as a difference…
We describe an instrument which can be used to analyze complex chemical mixtures at high resolution and high sensitivity. Molecules are collisionally cooled with helium gas at cryogenic temperatures (~ 4-7 K), and subsequently detected using chirped pulse microwave spectroscopy. Here we demonstrate three significant improvements to the apparatus relative to an earlier version: (1) extension of its operating range by more than a factor of two, from 12-18 GHz to 12-26 GHz, which allows a much wider range of species to be characterized; (2) improved detection sensitivity owing to use of cryogenic…
Experimental values for the viscosity of the radioactive hydrogen isotopologue tritium are still unknown in literature. Existing values from ab initio calculations disregard quantum mechanic effects and are therefore only good approximations for room temperature and above. To fill in these missing experimental values, a measurement setup has been designed, to measure the viscosity of gaseous hydrogen and its isotopologues (H$_2$, HD, HT, D$_2$, DT, T$_2$) at cryogenic temperatures. In this paper, the first results with this Cryogenic Viscosity Measurement Apparatus (Cryo-ViMA) of the viscosity…
As noble liquid time projection chambers grow in size their high voltage requirements increase, and detailed, reproducible studies of dielectric breakdown and the onset of electroluminescence are needed to inform their design. The Xenon Breakdown Apparatus (XeBrA) is a 5-liter cryogenic chamber built to characterize the DC high voltage breakdown behavior of liquid xenon and liquid argon. Electrodes with areas up to 33~cm$^2$ were tested while varying the cathode-anode separation from 1 to 6~mm with a voltage difference up to 75~kV. A power-law relationship between breakdown field and electrode…
A new search for a permanent electric dipole moment (EDM) of the neutron is underway using ultracold neutrons produced and held in a bath of superfluid helium. Attaining the target sensitivity requires maintaining an electric field of several tens of kilovolts per centimeter across the experimental cell, which is nominally 7.5 cm wide and will contain about 4 liters of superfluid. The electrical properties of liquid helium are expected to be sufficient to meet the design goals, but little is known about these properties for volumes and electrode spacings appropriate to the EDM experiment. Furt…
In the G0 experiment, performed at Jefferson Lab, the parity-violating elastic scattering of electrons from protons and quasi-elastic scattering from deuterons is measured in order to determine the neutral weak currents of the nucleon. Asymmetries as small as 1 part per million in the scattering of a polarized electron beam are determined using a dedicated apparatus. It consists of specialized beam-monitoring and control systems, a cryogenic hydrogen (or deuterium) target, and a superconducting, toroidal magnetic spectrometer equipped with plastic scintillation and aerogel Cerenkov detectors, …
The PVLAS collaboration is presently assembling a new apparatus (at the INFN section of Ferrara, Italy) to detect vacuum magnetic birefringence (VMB). VMB is related to the structure of the QED vacuum and is predicted by the Euler-Heisenberg-Weisskopf effective Lagrangian. It can be detected by measuring the ellipticity acquired by a linearly polarised light beam propagating through a strong magnetic field. Using the very same optical technique it is also possible to search for hypothetical low-mass particles interacting with two photons, such as axion-like (ALP) or millicharged particles (MCP…
The neutron and its hypothetical mirror counterpart, a sterile state degenerate in mass, could spontaneously mix in a process much faster than the neutron $β$-decay. Two groups have performed a series of experiments in search of neutron - mirror-neutron ($n-n'$) oscillations. They reported no evidence, thereby setting stringent limits on the oscillation time $τ_{nn'}$. Later, these data sets have been further analyzed by Berezhiani et al.(2009-2017), and signals, compatible with $n-n'$ oscillations in the presence of mirror magnetic fields, have been reported. The Neutron Electric Dipole Momen…
We report on a new high resolution apparatus for measuring magnetostriction suitable for use at cryogenic temperatures in pulsed high magnetic fields which we have developed at the Hochfeld-Magnetlabor Dresden. Optical fibre strain gauges based on Fibre Bragg Gratings are used to measure the strain in small (~1mm) samples. We describe the implementation of a fast measurement system capable of resolving strains in the order of $10^{-7}$ with a full bandwidth of 47kHz, and demonstrate its use on single crystal samples of GdSb and GdSi.
We present the design of a next-generation experiment, n2EDM, currently under construction at the ultracold neutron source at the Paul Scherrer Institute (PSI) with the aim of carrying out a high-precision search for an electric dipole moment of the neutron. The project builds on experience gained with the previous apparatus operated at PSI until 2017, and is expected to deliver an order of magnitude better sensitivity with provision for further substantial improvements. An overview is given of the experimental method and setup, the sensitivity requirements for the apparatus are derived, and i…
We report on the Beam EDM experiment, which aims to employ a pulsed cold neutron beam to search for an electric dipole moment instead of the established use of storable ultracold neutrons. We present a brief overview of the basic measurement concept and the current status of our proof-of-principle Ramsey apparatus.
We describe a proposed experimental search for exotic spin-coupled interactions using a solid-state paramagnetic insulator. The experiment is sensitive to the net magnetization induced by the exotic interaction between the unpaired insulator electrons with a dense, non-magnetic mass in close proximity. An existing experiment has been used to set limits on the electric dipole moment of the electron by probing the magnetization induced in a cryogenic gadolinium gallium garnet sample on application of a strong electric field. With suitable additions, including a movable source mass, this experime…
A high sensitivity force sensor based on dielectric microspheres in vacuum, optically trapped by a single, upward-propagating laser beam, is described. Off-axis parabolic mirrors are used both to focus the 1064~nm trapping beam and to recollimate it to provide information on the horizontal position of the microsphere. The vertical degree of freedom is readout by forming an interferometer between the light retroreflected by the microsphere and a reference beam, hence eliminating the need for auxiliary beams. The focus of the trapping beam has a 1/e$^2$ radius of 3.2~$μ$m and small non-Gaussian …
We present the new spectrometer for the neutron electric dipole moment (nEDM) search at the Paul Scherrer Institute (PSI), called n2EDM. The setup is at room temperature in vacuum using ultracold neutrons. n2EDM features a large UCN double storage chamber design with neutron transport adapted to the PSI UCN source. The design builds on experience gained from the previous apparatus operated at PSI until 2017. An order of magnitude increase in sensitivity is calculated for the new baseline setup based on scalable results from the previous apparatus, and the UCN source performance achieved in 201…
Magnetic field uniformity is of the utmost importance in experiments to measure the electric dipole moment of the neutron. A general parametrization of the magnetic field in terms of harmonic polynomial modes is proposed, going beyond the linear-gradients approximation. We review the main undesirable effects of non-uniformities: depolarization of ultracold neutrons, and Larmor frequency shifts of neutrons and mercury atoms. The theoretical predictions for these effects were verified by dedicated measurements with the single-chamber nEDM apparatus installed at the Paul Scherrer Institute.
The neutron's permanent electric dipole moment $d_n$ is constrained to below $3\times10^{-26} e~\text{cm}$ (90% C.L.) [ arXiv:hep-ex/0602020, arXiv:1509.04411 ], by experiments using ultracold neutrons (UCN). We plan to improve this limit by an order of magnitude or more with PanEDM, the first experiment exploiting the ILL's new UCN source SuperSUN. SuperSUN is expected to provide a high density of UCN with energies below 80 neV, implying extended statistical reach with respect to existing sources, for experiments that rely on long storage or spin-precession times. Systematic errors in PanEDM …
We present for the first time a detailed and comprehensive analysis of the experimental results that set the current world sensitivity limit on the magnitude of the electric dipole moment (EDM) of the neutron. We have extended and enhanced our earlier analysis to include recent developments in the understanding of the effects of gravity in depolarizing ultracold neutrons (UCN); an improved calculation of the spectrum of the neutrons; and conservative estimates of other possible systematic errors, which are also shown to be consistent with more recent measurements undertaken with the apparatus.…
