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.

Pressurized rf cavities in ionizing beams

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 ${\mathrm{SF}}_{6}$ and ${\mathrm{O}}_{2}$ were measured.

/pdf/pressurized-rf-cavities-in-ionizing-beams-rm14of0d4y.pdf

MANX is a 6-dimensional muon ionization-cooling experiment that has been proposed to Fermilab to demonstrate the use of a Helical Cooling Channel (HCC) for future muon colliders and neutrino factories. The HCC for MANX has solenoidal, helical dipole, and helical quadrupole magnetic components which diminish as the beam loses energy as it slow down in a liquid helium absorber inside the magnets. Additional magnets that provide emittance matching between the HCC and upstream and downstream spectrometers are also described as are the results of G4Beamline simulations of the beam cooling behavior of the complete magnet and absorber system.

/pdf/magnets-for-the-manx-6-d-muon-cooling-demonstration-3qdgec3lc5.pdf

Magnets for the MANX 6-D muon cooling demonstration experiment

The High Current Experiment (HCX) at Lawrence Berkeley National Laboratory is part of the US program that explores heavy-ion beam as the driver option for fusion energy production in an Inertial Fusion Energy (IFE) plant. The HCX is a beam transport experiment at a scale representative of the low-energy end of an induction linear accelerator driver. The primary mission of this experiment is to investigate aperture fill factors acceptable for the transport of space-charge-dominated heavy-ion beams at high intensity (line charge density {approx}0.2 {micro}C/m) over long pulse durations (4 {micro}s) in alternating gradient focusing lattices of electrostatic or magnetic quadrupoles. This experiment is testing transport issues resulting from nonlinear space-charge effects and collective modes, beam centroid alignment and steering, envelope matching, image charges and focusing field nonlinearities, halo and, electron and gas cloud effects. We present the results for a coasting 1 MeV K{sup +} ion beam transported through ten electrostatic quadrupoles. The measurements cover two different fill factor studies (60% and 80% of the clear aperture radius) for which the transverse phase-space of the beam was characterized in detail, along with beam energy measurements and the first halo measurements. Electrostatic quadrupole transport at high beam fill factor ({approx}80%) ismore » achieved with acceptable emittance growth and beam loss. We achieved good envelope control, and re-matching may only be needed every ten lattice periods (at 80% fill factor) in a longer lattice of similar design. We also show that understanding and controlling the time dependence of the envelope parameters is critical to achieving high fill factors, notably because of the injector and matching section dynamics.« less

/pdf/parametic-study-of-the-current-limit-within-a-single-driver-x6gxcgohbn.pdf

Parametic Study of the current limit within a single driver-scaletransport beam line of an induction Linac for Heavy Ion Fusion

MuCool 5T solenoid was successfully cooled down and operated coupled with MTA 'Brown' refrigerator The system performed as designed with substantial performance margin All process alarms and interlocks, as well as ODH and fire alarms, were active and performed as designed The cooldown of the refrigerator started from warm conditions and took 44 hours to accumulate liquid helium level and solenoid temperature below 5K Average liquid nitrogen consumption for the refrigerator precool and solenoid shield was measured as 20 gal/hr (including boil-off) Helium losses were small (below 30 scfh) The system was stable and with sufficient margin of performance and ran stably without wet expansion engine Quench response demonstrated proper operation of the relieving devices and pointed to necessity of improving tightness of the relieving manifolds Boil-off test demonstrated average heat load of 3 Watts for the unpowered solenoid The solenoid can stay up to 48 hours cold and minimally filled if the nitrogen shield is maintained A list of improvements includes commencing into operations the second helium compressor and completion of improvements and tune-ups for system efficiency

/pdf/commissioning-report-of-the-mucool-5-tesla-solenoid-coupled-3eyzvqzwgv.pdf

Commissioning report of the MuCool 5 Tesla solenoid coupled with helium refrigerator

There is an on going international collaboration studying the feasibility and cost of building a muon collider or neutrino factory [1,2]. An important aspect of this study is the full understanding of ionization cooling of muons by many orders of magnitude for the collider case. An important muon ionization cooling experiment, MICE [3], has been proposed to demonstrate and validate the technology that could be used for cooling. Ionization cooling is accomplished by passing a high-emittance muon beam alternately through regions of low Z material, such as liquid hydrogen, and very high accelerating RF Cavities within a multi-Tesla solenoidal field. To determine the effect of very large solenoidal magnetic fields on the generation of dark current, x-rays and on the breakdown voltage gradients of vacuum RF cavities, a test facility has been established at Fermilab in Lab G. This facility consists of a 12 MW 805 MHz RF station and a large warm bore 5 T solenoidal superconducting magnet containing a pill box type cavity with thin removable window apertures. This system allows dark current and breakdown studies of different window configurations and materials. The results of this study will be presented. The study has shown that the peak achievable more » accelerating gradient is reduced by a factor greater than 2 when solenoidal field of greater than 2 T are applied to the cavity. « less

/pdf/effect-of-high-solenoidal-magnetic-fields-on-breakdown-5clmz5xqg6.pdf

Effect of high solenoidal magnetic fields on breakdown voltages of high vacuum 805 MHz cavities

The initial phase of civil construction has begun on a new Linac Experimental Facility at Fermilab with beneficial occupancy anticipated in fall, 2003. This facility is being designed for multipurpose use by establishing direct and independent control over incident beam parameters; for example, pulse duration from 1 - 50 /spl mu/sec, and beam transverse sizes from 1 15 cm (95% of beam). The facility will be capable of accepting up to the full Fermilab Linac beam intensity (1.6 /spl times/ 10/sup 13/ protons/pulse @ 15 Hz) making it one of the few areas where a primary beam is available for high intensity experiments. The purpose of the facility initially is to test the basic techniques and components proposed for muon ionization cooling in a proton beam judged equivalent in impact to a muon beam for a Neutrino Factory or Muon Collider. As such, the facility will provide the advanced cryogenic capability and safety systems required to perform R&D on liquid hydrogen targets. However, parallel future experiments are invited and, as a general facility, many areas of physics including radiation, medical, nuclear, atomic and beam diagnostics and control will be supported.

The Mucool Test Area Linac Experimental Facility at Fermilab

There is an on going international collaboration studying the feasibility and cost of building a muon collider or neutrino factory [1,2]. An important aspect of this study is the full understanding of ionization cooling of muons by many orders of magnitude for the collider case. An important muon ionization cooling experiment, MICE [3], has been proposed to demonstrate and validate the technology that could be used for cooling. Ionization cooling is accomplished by passing a high-emittance muon beam alternately through regions of low Z material, such as liquid hydrogen, and very high accelerating RF Cavities within a multi-Tesla solenoidal field. To determine the effect of very large solenoidal magnetic fields on the generation of dark current, x-rays and on the breakdown voltage gradients of vacuum RF cavities, a test facility has been established at Fermilab in Lab G. This facility consists of a 12 MW 805 MHz RF station and a large warm bore 5 T solenoidal superconducting magnet containing a pill box type cavity with thin removable window apertures. This system allowes dark current and breakdown studies of different window configurations and materials. The results of this study will be presented. The study has shown that the peak achievable accelerating gradient is reduced by a factor greater than 2 when solenoidal field of greater than 2 T are applied to the cavity.

/pdf/effect-of-high-solenoidal-magnetic-fields-on-breakdown-5djwbc2n58.pdf

Effect of high solenoidal magnetic fields on breakdown

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Effect of high solenoidal magnetic fields on breakdown voltages of high vacuum 805 MHz cavities

The Mucool Test Area Linac Experimental Facility at Fermilab

Effect of high solenoidal magnetic fields on breakdown