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Neutrino Factory/Muon Collider Document 17-v1

Considerations for the Vacuum System of a 1.3 m Accelerating Structure for the Muon Cooling Channel

Document #:
NFMCC-doc-17-v1
Document type:
MuCool Note
Submitted by:
John Urish
Updated by:
John Urish
Document Created:
20 Jan 1999, 12:00
Contents Revised:
20 Jan 1999, 12:00
Metadata Revised:
20 Jan 1999, 12:00
Actually Revised:
14 Sep 2006, 13:35
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Abstract:

Considerations for the Vacuum System of a
1.3 m Accelerating Structure for the Muon
Cooling Channel

(Norbert Holtkamp, FNAL)

In any scheme for a muon collider the preparation of the muons has to be done as soon as
possible due to the finite lifetime of the muon [1]. Therefore the production, the capture,
the cooling and the acceleration requires high gradient rf structures (generally above 20
MV/m in a frequency range of 0.03 to 1.0 GHz. In the cooling channel low energy muons
(??2, ??0.85) travel through absorbing material and loose transverse and longitudinal
momentum. In the accelerating rf structures only longitudinal momentum is replaced
which results in a reduction in transverse phase space (transverse cooling). High gradient
805 MHz rf-structures are foreseen which operate at a gradient well above 30 MV/m and
at a duty cycle mainly given by the filling time of the structure and the pulse repetition
rate. The technical design of the structure is presented in [2]. One of the specialties of the
structure is a 125 ?m beryllium window, build into each iris, to increase the electric field
strength on axis (Epeak = Eacc). As a result, the coupling between the cells has to be
provided by an additional coupling cavity and the vacuum pumping by an outside
connected vacuum pipe. The latter, in combination with the operational requirements,
leads to certain restrictions for the vacuum system.
In recent years high gradient acceleration has been investigated in detail by several
groups working on linear collider design studies in order to understand the basic
limitations and possible improvements for future large scale high gradient linacs [3]. As
already known from super-conducting rf-accelerating cavity production, clean room type
assembly techniques are as necessary as excellent vacuum conditions to reduce
processing time and achieve routinely high gradients for operation.
Geometric constraints given by the cooling channel environment, as for example
15 Tesla super-conducting solenoids surrounding the accelerating structure with the
smallest possible bore, imply additional restrictions on waveguide feeds, water cooling-
and vacuum pumping connections.

Posted muc0017.ps to WWW
Posted by holtkamp

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Keywords:
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Notes and Changes:
Norbert Holtkamp
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