arXiv subjects

Joshua C. Long

Publications and source records attributed to Joshua C. Long.

5 recordsLinked to original sources

arXiv2003

Current Short-Range Tests of the Gravitational Inverse Square Law

Motivated in large part by the possibility of observing signatures of compact extra dimensions, experimental searches for deviations from Newtonian gravity at short distances have improved in sensitivity by many orders of magnitude in the past five years. We review the essential features of the experiments responsible for the current limits on new effects in the range from a few microns to a few centimeters, and discuss prospects for the near future.

hep-ph↗

arXiv2003

New Experimental Limits on Macroscopic Forces Below 100 Microns

Results of an experimental search for new macroscopic forces with Yukawa range between 5 and 500 microns are presented. The experiment uses 1 kHz mechanical oscillators as test masses with a stiff conducting shield between them to suppress backgrounds. No signal is observed above the instrumental thermal noise after 22 hours of integration time. These results provide the strongest limits to date between 10 and 100 microns, improve on previous limits by as much as three orders of magnitude, and rule out half of the remaining parameter space for predictions of string-inspired models with low-energy supersymmetry breaking. New forces of four times gravitational strength or greater are excluded at the 95% confidence level for interaction ranges between 200 and 500 microns.

hep-ph↗

arXiv2000

Gravitational Experiment Below 1 Millimeter and Comment on Shielded Casimir Backgrounds for Experiments in the Micron Regime

We present the status of an experimental test for gravitational strength forces below 1 mm. Our experiment uses small 1 kilohertz oscillators as test masses, with a stiff counducting shield between them to suppress backgrounds. At the present sensitivity of approximately 1000 times gravitational strength, we see no evidence for new forces with interaction ranges between 75 microns and 1 mm. While the Casimir background is not expected to be significant at this range, an extension of the shielding technique we employ may be useful for reducing this background in experiments below a few microns. We describe a possible implementation.

hep-ph↗

arXiv1999

Experimental Status of Gravitational-Strength Forces in the Sub-Centimeter Regime

We review the experimental constraints on additional macroscopic Yukawa forces for interaction ranges below 1 cm., and summarize several theoretical predictions of new forces in this region. An experiment using 1 kHz mechanical oscillators as test masses should be sensitive to much of the parameter space covered by the predictions.

hep-ph↗

arXiv1998

Taber Vibration Isolator for Vacuum and Cryogenic Applications

We present a procedure for the design and construction of a passive, multipole, mechanical high-stop vibration isolator. The isolator, consisting of a stack of metal disks connected by thin wires, attenuates frequencies in the kilohertz range, and is suited to both vacuum and cryogenic environments. We derive an approximate analytical model and compare its predictions for the frequencies of the normal modes to those of a finite element analysis. The analytical model is exact for the modes involving only motion along and rotation about the longitudinal axis, and it gives a good approximate description of the transverse modes. These results show that the high-frequency behavior of a multi-stage isolator is well characterized by the natural frequencies of a single stage. From the single-stage frequency formulae, we derive relationships among the various geometrical parameters of the isolator to guarantee equal attenuation in all degrees of freedom. We then derive expressions for the attenuation attainable with a given isolator length, and find that the most important limiting factor is the elastic limit of the spring wire material. For our application, which requires attenuations of 250 dB at 1 kHz, our model specifies a six-stage design using brass disks of approximately 2 cm in both radius and thickness, connected by 3 cm steel wires of diameters ranging from 25 to 75 microns. We describe the construction of this isolator in detail, and compare measurements of the natural frequencies of a single stage with calculations from the analytical model and the finite element package. For translations along and rotations about the longitudinal axes, all three results are in agreement to within 10% accuracy.

physics.ins-det↗