A major technological challenge in building a muon cooling channel is operating rf cavities in multitesla external magnetic fields. We report the first proof-of-principle experiment of a high ...pressure gas-filled rf cavity for use with intense ionizing beams and strong external magnetic fields. rf power consumption by beam-induced plasma is investigated with hydrogen and deuterium gases with pressures between 20 and 100 atm and peak rf gradients between 5 and 50 MV/m. The low pressure case agrees well with an analytical model based on electron and ion mobilities. Varying concentrations of oxygen gas are investigated to remove free electrons from the cavity and reduce the rf power consumption. Measurements of the electron attachment time to oxygen and rate of ion-ion recombination are also made. Additionally, we demonstrate the operation of the gas-filled rf cavity in a solenoidal field of up to 3 T, finding no major magnetic field dependence. All these results indicate that a high pressure gas-filled cavity is a viable technology for muon ionization cooling.
Pressurized rf cavities in ionizing beams Freemire, B.; Tollestrup, A. V.; Yonehara, K. ...
Physical review. Accelerators and beams,
06/2016, Letnik:
19, Številka:
6
Journal Article
Recenzirano
Odprti dostop
A muon collider or Higgs factory requires significant reduction of the six dimensional emittance of the beam prior to acceleration. One method to accomplish this involves building a cooling channel ...using high pressure gas filled radio frequency cavities. The performance of such a cavity when subjected to an intense particle beam must be investigated before this technology can be validated. To this end, a high pressure gas filled radio frequency (rf) test cell was built and placed in a 400 MeV beam line from the Fermilab linac to study the plasma evolution and its effect on the cavity. Hydrogen, deuterium, helium and nitrogen gases were studied. Additionally, sulfur hexafluoride and dry air were used as dopants to aid in the removal of plasma electrons. Measurements were made using a variety of beam intensities, gas pressures, dopant concentrations, and cavity rf electric fields, both with and without a 3 T external solenoidal magnetic field. Energy dissipation per electron-ion pair, electron-ion recombination rates, ion-ion recombination rates, and electron attachment times to SF6 and O2 were measured.
Viability of BSCCO-2212 round wires for high field magnet applications is being investigated within the Very High Field Superconducting Magnet Collaboration (VHFSMC). Three BSCCO-2212 wires of ...different designs were homogeneously flat-rolled to decreasing sizes to study the effect of deformation as a function of the precursor used and of the architecture parameters of the wires. After heat treatment at Oxford Superconducting Technology (OST), size variations of round and deformed samples were measured, and their transport properties characterized at 4.2 K and at magnetic fields up to 14 T. The wire made with granulate precursor was the most homogenous. The wires made with powder precursor showed instead non-monotonic behavior in I c and even more so in the n-value.
Beam-beam effects in the Tevatron Shiltsev, V.; Alexahin, Y.; Lebedev, V. ...
Physical review special topics. PRST-AB. Accelerators and beams,
10/2005, Letnik:
8, Številka:
10
Journal Article
Recenzirano
Odprti dostop
The Tevatron in Collider Run II (2001–present) is operating with 6 times more bunches, many times higher beam intensities and luminosities than in Run I (1992–1995). Electromagnetic long-range and ...head-on interactions of high intensity proton and antiproton beams have been significant sources of beam loss and lifetime limitations. We present observations of the beam-beam phenomena in the Tevatron and results of relevant beam studies. We analyze the data and various methods employed in operations, predict the performance for planned luminosity upgrades, and discuss ways to improve it.
The measurement of the longitudinal behavior of the accelerated particle beams at Fermilab is crucial to the optimization and control of the beam and the maximizing of the integrated luminosity for ...the particle physics experiments. Longitudinal measurements in the Tevatron and Main Injector synchrotrons are based on the analysis of signals from resistive wall current monitors. This article describes the signal processing performed by a 2 GHz-bandwidth oscilloscope together with a computer running a LabVIEW program which calculates the longitudinal beam parameters.
Male volunteers
(
N
= 120)
in small groups of 5 to 10 watched a staged theft involving live actors. Some
(
n
= 47)
were under the influence of alcohol (average blood alcohol level of .10) at the ...time. Some subjects
(
n
= 58)
were interviewed immediately after the event, and all were interviewed 1 week later. The delayed interview included the presentation of a photospread that either did or did not contain the picture of the "thief." Alcohol suppressed the amount recalled during the immediate interview and both the amount and accuracy of recall after the 1-week delay. Alcohol had no influence on the ability of witnesses to recognize the thief's picture. When the thief's picture was not present in the photospread, however, alcohol increased the rate of false identifications. An immediate interview substantially improved the amount of information subjects were able to recall 1 week later.
A major technological challenge in building a muon cooling channel is operating RF cavities in multi-tesla external magnetic fields. We report the first experimental characterization of a high ...pressure gas-filled 805 MHz RF cavity for use with intense ionizing beams and strong external magnetic fields. RF power consumption by beam-induced plasma was investigated with hydrogen and deuterium gases with pressures between 20 and 100 atm and peak RF gradients between 5 and 50 MV/m. The energy absorption per ion pair-RF cycle ranges from 10-18 to 10-16 J. The low pressure case agrees well with an analytical model based on electron and ion mobilities. Varying concentrations of oxygen gas were investigated to remove free electrons from the cavity and reduce the RF power consumption. Measurements of the electron attachment time to oxygen and rate of ion-ion recombination were also made. Additionally, we demonstrate the operation of the gas-filled RF cavity in a solenoidal field of up to 3 T, finding no major magnetic field dependence. These results indicate that a high pressure gas-filled cavity is potentially a viable technology for muon ionization cooling.
In this article we present results of emittance growth measurements in the Tevatron beams. Several mechanisms leading to transverse and longitudinal diffusions are analyzed and their contributions ...estimated.
A muon collider or Higgs factory requires significant reduction of the six dimensional emittance of the beam prior to acceleration. One method to accomplish this involves building a cooling channel ...using high pressure gas filled radio frequency cavities. The performance of such a cavity when subjected to an intense particle beam must be investigated before this technology can be validated. To this end, a high pressure gas filled radio frequency (rf) test cell was built and placed in a 400 MeV beam line from the Fermilab linac to study the plasma evolution and its effect on the cavity. Hydrogen, deuterium, helium and nitrogen gases were studied. Additionally, sulfur hexafluoride and dry air were used as dopants to aid in the removal of plasma electrons. Measurements were made using a variety of beam intensities, gas pressures, dopant concentrations, and cavity rf electric fields, both with and without a 3 T external solenoidal magnetic field. Energy dissipation per electron-ion pair, electron-ion recombination rates, ion-ion recombination rates, and electron attachment times to \(SF_6\) and \(O_2\) were measured.
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