33 research outputs found
An Underappreciated Radiation Hazard from High Voltage Electrodes in Vacuum
The use of high voltage (HV) electrodes in vacuum is commonplace in physics
laboratories. In such systems, it has long been known that electron emission
from an HV cathode can lead to bremsstrahlung X-rays; indeed, this is the basic
principle behind the operation of standard X-ray sources. However, in
laboratory setups where X-ray production is not the goal and no electron source
is deliberately introduced, field-emitted electrons accelerated by HV can
produce X-rays as an unintended hazardous byproduct. Both the level of hazard
and the safe operating regimes for HV vacuum electrode systems are not widely
appreciated, at least in university laboratories. A reinforced awareness of the
radiation hazards associated with vacuum HV setups would be beneficial. We
present a case study of a HV vacuum electrode device operated in a university
atomic physics laboratory. We describe the characterisation of the observed
X-ray radiation, its relation to the observed leakage current in the device,
the steps taken to contain and mitigate the radiation hazard, and suggest
safety guidelines.Comment: Submitted to Health Physic
The metastable Q state of ThO: A new resource for the ACME electron EDM search
The best upper limit for the electron electric dipole moment was recently set
by the ACME collaboration. This experiment measures an electron spin-precession
in a cold beam of ThO molecules in their metastable state.
Improvement in the statistical and systematic uncertainties is possible with
more efficient use of molecules from the source and better magnetometry in the
experiment, respectively. Here, we report measurements of several relevant
properties of the long-lived state of ThO, and show that this
state is a very useful resource for both these purposes. The state lifetime
is long enough that its decay during the time of flight in the ACME beam
experiment is negligible. The large electric dipole moment measured for the
state, giving rise to a large linear Stark shift, is ideal for an electrostatic
lens that increases the fraction of molecules detected downstream. The measured
magnetic moment of the state is also large enough to be used as a sensitive
co-magnetometer in ACME. Finally, we show that the state has a large
transition dipole moment to the state, which allows for efficient
population transfer between the ground state and the state
via Stimulated Raman Adiabatic Passage (STIRAP). We demonstrate %
STIRAP transfer efficiency. In the course of these measurements, we also
determine the magnetic moment of state, the transition
dipole moment, and branching ratios of decays from the state.Comment: 21 pages, 6 figures, 5 pages appendice
Suppression of the optical crosstalk in a multi-channel silicon photomultiplier array
We propose and study a method of optical crosstalk suppression for silicon photomultipliers (SiPMs) using optical filters. We demonstrate that attaching absorptive visible bandpass filters to the SiPM can substantially reduce the optical crosstalk. Measurements suggest that the absorption of near infrared light is important to achieve this suppression. The proposed technique can be easily applied to suppress the optical crosstalk in SiPMs in cases where filtering near infrared light is compatible with the application
A cryogenic beam of refractory, chemically reactive molecules with expansion cooling
Cryogenically cooled buffer gas beam sources of the molecule thorium monoxide
(ThO) are optimized and characterized. Both helium and neon buffer gas sources
are shown to produce ThO beams with high flux, low divergence, low forward
velocity, and cold internal temperature for a variety of stagnation densities
and nozzle diameters. The beam operates with a buffer gas stagnation density of
~10^15-10^16 cm^-3 (Reynolds number ~1-100), resulting in expansion cooling of
the internal temperature of the ThO to as low as 2 K. For the neon (helium)
based source, this represents cooling by a factor of about 10 (2) from the
initial nozzle temperature of about 20 K (4 K). These sources deliver ~10^11
ThO molecules in a single quantum state within a 1-3 ms long pulse at 10 Hz
repetition rate. Under conditions optimized for a future precision spectroscopy
application [A C Vutha et al 2010 J. Phys. B: At. Mol. Opt. Phys. 43 074007],
the neon-based beam has the following characteristics: forward velocity of 170
m/s, internal temperature of 3.4 K, and brightness of 3x10^11 ground state
molecules per steradian per pulse. Compared to typical supersonic sources, the
relatively low stagnation density of this source, and the fact that the cooling
mechanism relies only on collisions with an inert buffer gas, make it widely
applicable to many atomic and molecular species, including those which are
chemically reactive, such as ThO
Advanced cold molecule electron EDM
Measurement of a non-zero electric dipole moment (EDM) of the electron within a few orders of magnitude of the current best limit of |d_e| < 1.05 × 10^(−27) e⋅cm [1] would be an indication of physics beyond the Standard Model. The ACME Collaboration is searching for an electron EDM by performing a precision measurement of electron spin precession in the metastable H^3Δ_1 state of thorium monoxide (ThO) using a slow, cryogenic beam. We discuss the current status of the experiment. Based on a data set acquired from 14 hours of running time over a period of 2 days, we have achieved a 1-sigma statistical uncertainty of δd_e = 1 × 10^(−28) e⋅cm/√T, where T is the running time in days
Macroscopic quantum resonators (MAQRO)
Quantum physics challenges our understanding of the nature of physical
reality and of space-time and suggests the necessity of radical revisions of
their underlying concepts. Experimental tests of quantum phenomena involving
massive macroscopic objects would provide novel insights into these fundamental
questions. Making use of the unique environment provided by space, MAQRO aims
at investigating this largely unexplored realm of macroscopic quantum physics.
MAQRO has originally been proposed as a medium-sized fundamental-science space
mission for the 2010 call of Cosmic Vision. MAQRO unites two experiments:
DECIDE (DECoherence In Double-Slit Experiments) and CASE (Comparative
Acceleration Sensing Experiment). The main scientific objective of MAQRO, which
is addressed by the experiment DECIDE, is to test the predictions of quantum
theory for quantum superpositions of macroscopic objects containing more than
10e8 atoms. Under these conditions, deviations due to various suggested
alternative models to quantum theory would become visible. These models have
been suggested to harmonize the paradoxical quantum phenomena both with the
classical macroscopic world and with our notion of Minkowski space-time. The
second scientific objective of MAQRO, which is addressed by the experiment
CASE, is to demonstrate the performance of a novel type of inertial sensor
based on optically trapped microspheres. CASE is a technology demonstrator that
shows how the modular design of DECIDE allows to easily incorporate it with
other missions that have compatible requirements in terms of spacecraft and
orbit. CASE can, at the same time, serve as a test bench for the weak
equivalence principle, i.e., the universality of free fall with test-masses
differing in their mass by 7 orders of magnitude.Comment: Proposal for a medium-sized space mission, 28 pages, 9 figures - in
v2, we corrected some minor mistakes and replaced fig. 9 with a
higher-resolution version; Experimental Astronomy, March 2012, Online, Open
Acces
Electric dipole moments and the search for new physics
Static electric dipole moments of nondegenerate systems probe mass scales for
physics beyond the Standard Model well beyond those reached directly at high
energy colliders. Discrimination between different physics models, however,
requires complementary searches in atomic-molecular-and-optical, nuclear and
particle physics. In this report, we discuss the current status and prospects
in the near future for a compelling suite of such experiments, along with
developments needed in the encompassing theoretical framework.Comment: Contribution to Snowmass 2021; updated with community edits and
endorsement
2014 Progress Report by the Antihydrogen TRAP Collaboration (ATRAP)
2014 Progress Report by the Antihydrogen TRAP Collaboration (ATRAP) submitted for the 116th meeting of the SPS