CERN NFWG PROPOSAL
C. D. Johnson       09/99

To study the behaviour of a high-power RF Cavity in a high-intensity pulsed radiation field

This tentative proposal is designed to provide information on the behaviour of an RF cavity in a high radiation field prior to the muon targetry and capture experiment now proposed at BNL:  "A Proposal for an R&D Program for Targetry and Capture at a Muon-Collider Source"   BNL proposal P951    The CERN antiproton production beam will be in use for some years as a source of antiprotons for the Antiproton Decelerator. The target area was designed as a high-radiation zone for antiproton production at the time of the SPS collider experiments. It is equipped with some remote handling tools and has various facilities for R&D work on targetry and secondary particle collection (e.g. cable conduits from the surface buildings, tv cameras, personnel observation shelters). A selected momentum bite of secondary particles is transported to the AD machine hall via a 'dogleg' beamline. The uninteracting proton beam, together with a the majority of the secondary radiation flux is dumped in water-cooled aluminium blocks approximately 10 m downstream from the target. At this position - in front of the dump - there is convenient space for carrying out irradiation tests on fairly bulky objects. The secondary beamline crosses in front of this space, but the beam is in air and so there is no vacuum pipe to hinder access. The radiation dose rates and hadron fluxes are well known from calculation and from many direct measurements made by TIS Division.

                Plan of installation

The CERN PS can deliver a beam onto the antiproton target with the following properties:
      - up to 4 bunches spaced by 105 ns
      - bunch length (4sz) of 25 ns
      - intensity up to a maximum of 5x1012 p/bunch or 7x1012 p/bunch in single-bunch mode.

The target is Iridium of 1 interaction length, but it can be removed if desired. The collimator downstream of the target has a large aperture (120 mm diameter) and so the secondary radiation from the target would illuminate a disc of ~1m diameter at the dump, which is just about right for the irradiaton of a low frequency cavity (~200 MHz). The magnetic horn would be switched off, since it would serve little purpose, unless one wished to alter the charge ratio in the secondary flux. That might, in fact, be interesting! An option would be to remove the primary target and to place a temporary target, of say 3 interaction lengths, 1 to 2 m upstream of the cavity (at the same position). The proton beam could be re-focused to a spot size of ~ 1cm diameter at this target. The advantage of the first scenario is that we could run parasitically during AD fills. But the second option could probably be accommodated in the AD program without much difficulty

                Photo mock-up of installation

To further study this proposal we should:
      - review the status of the remote handling equipment in the AD Target Area
      - select a cavity for these tests - a simple pill-box cavity is indicated (frequency to be chosen in the range 100 to 500 MHz)
      - study the power requirements and diagnostics
      - prepare radiation and hadron flux maps for the region immediately upstream of the beam dump.

This could be an exercise for the NFWG in the coming months.