108754068
SRF cavity testing status and operating experience
The cryogenic system at the Meson Detector Building (MDB) has now supported over four years of testing of fully assembled SRF cavities. The Horizontal Test Stand (HTS) has tested single, fully dressed 1.3 GHz and 3.9 GHz cavities at 2 K as final qualification prior to their installation into accelerator-ready cryomodules. The MDB cryogenic system has been expanded to support an additional cavity test area, the Spoke Resonator Test (SRT) area, for 325 MHz single-spoke resonators. The SRT area currently supports 4.5 K operations for research and development of the spoke cavities with tuner and coupler. The test area addition required the design and installation of a new cryogenic transfer line extension to reach this second test area and to allow for independent operations of either cavity test system. The cryogenic performance and operational experiences of both cavity test areas, operating individually or simultaneously, will be discussed. The general reliability of operating the closed, subatmospheric he...
109984057
Fermilab SRF cryomodule operational experience
Fermi National Accelerator Laboratory is constructing an Advanced Accelerator Research and Development facility at New Muon Lab. The cryogenic infrastructure in support of the initial phase of the facility consists of two Tevatron style standalone refrigerators, cryogenic distribution system as well as an ambient temperature pumping system to achieve 2 K operations with supporting purification systems. During this phase of the project a single Type III plus 1.3 GHz cryomodule was installed, cooled and tested. Design constraints of the cryomodule required that the cryomodule individual circuits be cooled at predetermined rates. These constraints required special design solutions to achieve. This paper describes the initial cooldown and operational experience of a 1.3 GHz cryomodule using the New Muon Lab cryogenic system.
119232009
Plate fin heat exchanger model with axial conduction and variable properites
Future superconduction radio frequency (SRF) cavities, as part of Project X at Fermilab,will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchanger are an effective option. However, at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numberical model that includes the effects of axial guide design decisions on heat exhanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger to analyze the effect of heat load and cryogenic supply parameters.
109689468
Spallation neutron source (SNS)
The Spallation Neutron Source [1], located at Oak Ridge, TN, is a state-of-the-art neutron-scattering facility presently under construction as a collaborative effort of six national laboratories. The facility is comprised of a high-power particle-accelerator system, a liquid-mercury target-moderator system, and a suite of world-class scientific instruments. One-ms-long negative-hydrogen-ion (H - ) pulses are produced by an ion source. The ion beam is accelerated to 185 MeV by normal conducting (NC) linear accelerator (linac) cavities, and further accelerated to 1 GeV by a superconducting linac [2]. The acceleration is accomplished by means of niobium superconducting radiofrequency (SRF) cavities that operate at 2.1K. The linac beam is stacked in a compressor ring, and 695-ns-long pulses are extracted onto the target at a 60-Hz rate. Neutrons are produced by spallation in the mercury, and their energy is moderated to useable levels, in part by supercritical hydrogen moderators. The simultaneous performance goals of more than one MW of initial proton beam power, 95% facility availability, and the desire for hands-on maintenance capability in the accelerator complex place significant demands on the performance and operational reliability of the technical and conventional systems. An overview of the SNS facility, including its purpose, major components, and a summary of the present status is presented, with particular emphasis on the superconducting linac and the cryogenic moderators.
123909158
DESIGN AND OPERATION OF THE PRINCETON-PENNSYLVANIA PROTON SYNCHROTRON
The 16 sector magnet is weak focusing with n = 0.6 over a useful radial region of 16.5 cm and 6.1 cm vertically. A d-c biased, sine wave excitation at 19 cps is employed, the energy storage being in a resonant capacitor-inductor system. Injection at 3 Mev is provided by an electrostatic generator. Acceleration is achieved by a combination of drift tubes and resonant cavities which must provide 120 kv per turn, and must be precisely tuned over a 12: 1 range in frequency. To date, 2 x 10/sup 10/ protons per pulse have been injected, of which about 10% are captured by the r-f. A method for extracting the proton beam, which is similar to Piccionis' system, but freer of aberrations, is now under design. (auth)
119457260
Detecting near ultraviolet radiation in the presence of visible light
We describe a system which suppresses the detection of visible sodium vapor light by a factor of about 108 relative to near ultraviolet radiation.
42216143
Fast supersymmetry phenomenology at the Large Hadron Collider using machine learning techniques
A pressing problem for supersymmetry (SUSY) phenomenologists is how to incorporate Large Hadron Collider search results into parameter fits designed to measure or constrain the SUSY parameters. Owing to the computational expense of fully simulating lots of points in a generic SUSY space to aid the calculation of the likelihoods, the limits published by experimental collaborations are frequently interpreted in slices of reduced parameter spaces. For example, both ATLAS and CMS have presented results in the Constrained Minimal Supersymmetric Model (CMSSM) by fixing two of four parameters, and generating a coarse grid in the remaining two. We demonstrate that by generating a grid in the full space of the CMSSM, one can interpolate between the output of an LHC detector simulation using machine learning techniques, thus obtaining a superfast likelihood calculator for LHC-based SUSY parameter fits. We further investigate how much training data is required to obtain usable results, finding that approximately 2000 points are required in the CMSSM to get likelihood predictions to an accuracy of a few per cent. The techniques presented here provide a general approach for adding LHC event rate data to SUSY fitting algorithms, and can easily be used to explore other candidate physics models.
1938181
Determining SUSY model parameters and masses at the LHC using cross-sections, kinematic edges and other observables.
We address the problem of mass measurements of supersymmetric particles at the Large Hadron Collider, using the ATLAS detector as an example. By using Markov Chain sampling techniques to combine standard measurements of kinematic edges in the invariant mass distributions of decay products with a measurement of a missing pT cross-section, we show that the precision of mass measurements at the LHC can be dramatically improved, even when we do not assume that we have measured the kinematic endpoints precisely, or that we have identified exactly which particles are involved in the decay chain causing the endpoints. The generality of the technique is demonstrated in a preliminary investigation of a non-universal SUGRA model, in which we relax the requirements of mSUGRA by breaking the degeneracy of the GUT scale gaugino masses. The model studied is compatible with the WMAP limits on dark matter relic density.