Direct observation of microwaves excited in the Fermilab beam pipe by very narrow bunches

Conference · Tue Oct 01 04:00:00 EDT 1985 · IEEE Trans. Nucl. Sci.; (United States)

OSTI ID:6076642

Griffin, J E; MacLachlan, J A

The bunch rotation exchange of time for momentum spread in the Fermilab Antiproton Source is dependent upon proton bunch narrowing at 120 GeV in the Main Accelerator. The original procedure proposed to accomplish bunch narrowing involved adiabatic reduction of the Main Ring rf voltage (and bucket height) until the bunches span approximately + or -..pi../2 radians in the bucket, followed by a sudden increase in rf voltage causing bunch rotation within the now mismatched bucket and consequent bunch narrowing in time spread. This procedure suffers from several draw-backs. One fundamental problem is that during the adiabatic portion of the procedure the bunches are caused to have a very low momentum spread and to remain in this condition for many phase oscillation periods. In this circumstance the bunches may be subject to microwave instability which would limit the momentum spread reduction and consequently the final bunch length. A second problem with the procedure is simply that it requires an inordinately long time and may at some point limit the cycle time and consequently the antiproton production rate. Thirdly, since antiprotons are produced by a single batch of 83 bunches occupying only 1/13 of the 1113 Main Ring buckets, the beam quality during the long counterphasing period may suffer from imprecise compensation for transient beam loading of the rf system. When the voltage has been reduced to the very low value required to match the elongated bunch configuration, about 4 kappaV, the beam induced voltage may be comparable to that required to create the buckets, compensation notwithstanding.

• Research Organization: Fermi National Accelerator Laboratory, Batavia, IL
• OSTI ID: 6076642
• Report Number(s): CONF-850504-
• Conference Information: Journal Name: IEEE Trans. Nucl. Sci.; (United States) Journal Volume: NS-32:5
• Country of Publication: United States
• Language: English

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