Author: Leonova, M.A.
Paper Title Page
MOPPC036 Influence of Intense Beam in High Pressure Hydrogen Gas Filled RF Cavities 208
 
  • K. Yonehara, M.R. Jana, M.A. Leonova, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup
    Fermilab, Batavia, USA
  • M. Chung
    Handong Global University, Pohang, Republic of Korea
  • M.G. Collura
    Politecnico di Torino, Torino, Italy
  • G. Flanagan, R.P. Johnson, M. Notani
    Muons, Inc, Batavia, USA
  • B.T. Freemire, Y. Torun
    IIT, Chicago, Illinois, USA
 
  Funding: This work is supported by US DOE under contract DE-AC02-07CH11359.
Breakdown plasma in a high-pressure hydrogen gas filled RF cavity has been studied from a time domain spectroscopic light analysis. The observed breakdown plasma temperature and density reached 21,000 K and 1020 cm-3, respectively. The electron recombination rate has been evaluated from the decay of plasma density in various gas pressures. The recombination mechanism in dense plasma will be discussed. Finally, the similarity and difference of the breakdown processes between the high-pressure hydrogen gas filled RF cavity and a vacuum RF one will be discussed.
 
 
MOPPC039 Electron Recombination in a Dense Hydrogen Plasma 217
 
  • B.T. Freemire, P.M. Hanlet
    IIT, Chicago, Illinois, USA
  • M. Chung
    Handong Global University, Pohang, Republic of Korea
  • M.G. Collura
    Politecnico di Torino, Torino, Italy
  • M.R. Jana, C. Johnstone, T. Kobilarcik, G.M. Koizumi, M.A. Leonova, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup, Y. Torun, K. Yonehara
    Fermilab, Batavia, USA
  • R.P. Johnson
    Muons, Inc, Batavia, USA
 
  Funding: US DOE under contract DE-AC02-07CH11359.
A high pressure hydrogen gas filled RF cavity was subjected to an intense proton beam to study the evolution of the beam induced plasma inside the cavity. The electron recombination rate with the dense ionized hydrogen plasma has been measured under varying conditions. Recombination rates as high as 10-7 cm3/s have been recorded. This technique shows promise in the R&D program for a muon accelerator. The use of hydrogen, both as a way to prevent breakdown in an RF cavity and as a mechanism for cooling a beam of muons, will be discussed.
 
 
MOPPC040 Study of Electronegative Gas Effect in Beam-Induced Plasma 220
 
  • M.A. Leonova, M.R. Jana, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup, K. Yonehara
    Fermilab, Batavia, USA
  • M. Chung
    Handong Global University, Pohang, Republic of Korea
  • M.G. Collura
    Politecnico di Torino, Torino, Italy
  • B.T. Freemire, P.M. Hanlet, Y. Torun
    IIT, Chicago, Illinois, USA
  • R.P. Johnson
    Muons, Inc, Batavia, USA
 
  Funding: This research was supported by US DOE under contract DE-AC02-07CH11359.
Muon Colliders and Neutrino Factories call for R&D for a high-gradient RF system capable of operating in a high magnetic field. Adding a high pressure gas inside an RF cavity (HPRF) prevents cavity breakdown, allowing higher gradients in a magnetic field. A high-energy beam passing through an HPRF cavity ionizes the gas, producing plasma. Plasma electrons absorb cavity’s energy, reducing the energy available for beam acceleration. Doping cavity gas with electronegative gas (gas that tends to attract and bond electrons) reduces the number of plasma electrons. The experiments were carried out at the MuCool Test Area (MTA) facility at Fermilab. Different concentrations of an electronegative gas SF6 were added to hydrogen gas. The results of room-temperature tests showing a great reduction in power drop in the cavity will be presented. However, a realistic cavity would operate at liquid nitrogen temperature, where SF6 freezes. Thus, a search for a better electronegative gas candidate is underway; we plan to test oxygen-doping next.
 
 
WEOBA03 Beam Tests of a High Pressure Gas-Filled Cavity for a Muon Collider 2131
 
  • T.A. Schwarz, M.A. Leonova, A. Moretti, M. Popovic, A.V. Tollestrup, K. Yonehara
    Fermilab, Batavia, USA
  • M. Chung
    Handong Global University, Pohang, Republic of Korea
  • B.T. Freemire, P.M. Hanlet, Y. Torun
    IIT, Chicago, Illinois, USA
  • R.P. Johnson
    Muons, Inc, Batavia, USA
 
  Funding: US DOE under contract DE-AC02-07CH11359.
One of the greatest challenges in constructing a Muon Collider is cooling the hot muons into a focused beam after their production. Because the beam must be cooled quickly before the muons decay, compact cooling designs require high gradient cavities inside strong magnetic fields. Unfortunately, due to focused field emission, an external magnetic field degrades the performance of the cavity below what is required for a muon collider. High-pressure gas inside the cavity has been proposed to both mitigate this effect, as well as serve as an absorber for transversely cooling the muon beam. A prototype of a high pressure gas-filled cavity is currently being studied at the Muon Test Area at Fermilab. The experimental setup as well as several measurements of the physics and performance of the apparatus while operating in a 400-MeV proton beam will be discussed.
 
slides icon Slides WEOBA03 [6.912 MB]  
 
MOPPR070 Beam Profile Measurement in MTA Beam Line for High Pressure RF Cavity Beam Test 948
 
  • M.R. Jana, A.D. Bross, S. Geer, C. Johnstone, T. Kobilarcik, G.M. Koizumi, M.A. Leonova, A. Moretti, M. Popovic, T.A. Schwarz, A.V. Tollestrup, K. Yonehara
    Fermilab, Batavia, USA
  • M. Chung
    Handong Global University, Pohang, Republic of Korea
  • M.G. Collura
    Politecnico di Torino, Torino, Italy
  • B.T. Freemire, P.M. Hanlet, Y. Torun
    IIT, Chicago, Illinois, USA
 
  Funding: This work is supported by the United States Department of Energy under contract DE-AC02-07CH11359.
The recent High Pressure RF (HPRF) cavity experiment at the MuCool Test Area (MTA) used a 400 MeV Linac proton beam to study the beam loading effect. When the energetic proton beam passes through the cavity, it ionizes the inside gas and produces electrons. These electrons consume RF power inside the cavity. The number of electrons produced per cm inside the cavity (at 950 psi Hydrogen gas) per incident proton is 1200. The measurement of beam position and profile are necessary. The MTA is a flammable gas (Hydrogen) hazard zone, so we have developed a passive beam diagnostic instrument using a Chromox-6 scintillation screen and CCD camera. This paper presents quantitative information about beam position and beam profile. A neutral density filter was used to avoid saturation of the CCD camera. Image data is filtered and fitted with a Gaussian function to compute the beam size. The beam profile obtained from the scintillation screen will be compared with a multi-wire beam profile.