tuning ball from Brookhaven 50 MeV linac
notes: label: Description
content: Object 1997.0392.02 is a ball for tuning the 50 million volt linear accelerator that served as the first injector to the 33 billion volt Alternating Gradient Synchrotron for protons at the Brookhaven National Laboratory, circa 1962. It consists of a sphere of solid copper, with a threaded radial hole, and a hole of smaller diameter on the same axis continuing through to the surface opposite. It bears no markings.
label: Description
content: Cavity tuning in drift tube linacs
label: Description
content: It is not possible initially to build the linac cavities (cylindrical vacuum chambers with drift tubes) to achieve the design electric field frequency and distribution, because the drift tubes detune the frequencies of the cells (regions between centers of successive drift tube gaps). In each cell, the drift tubes decrease the volume available to the electric field at a region where it is strongest and at a region where the magnetic field is the weakest. Thus, tuning devices are often inserted into the cells to achieve a “flat” field.
label: Description
content: Field corrections are made with a combination of gross tuning and fine tuning. First, gross tuning is accomplished by inserting long copper bars of the appropriate size in the cavities. The effects of local cavity frequency variations can then be corrected by a series of devices located at discrete points along the cavity wall.
label: Description
content: Cavity tuning for the Brookhaven 50 MeV linac
label: Description
content: Correct resonance and flattening of the electric field were obtained by varying the penetrations of ball tuners in several cells of the linac cavity. There were five ball tuners (100 mm diameter). In practice the gross errors were first eliminated with a tuning bar fixed to the cavity wall. Fine tuning was then done by radial motion of the ball tuners whose positions were controllable from outside the tank. In later versions of the linac, the ball tuners were replaced with “slug” tuners. The slug-tuner design was favored over the ball tuner for two reasons: 1) greater tuning effect (or smaller tuner penetration, 2) a defective tuner could be replaced without entering the cavity or removing the end covers.) A cavity servo tuning system controlled any chosen combination of the five ball tuners.
label: Description
content: It is assumed that object 1997.0392.02, tuning ball, was part of such a ball tuning device for the Brookhaven 50 MeV linac.
label: Description
content: For more on the basic principles of cavity tuning in drift tube linacs, see the following web-based references:
label: Description
content: https://www.bnl.gov/cad/accelerator/docs/pdf/200MEV-ProtonLinearAcc.pdf
label: Description
content: https://lss.fnal.gov/archive/other/mura/MURA-723.pdf
label: Description
content: For more on linac drift tube basics, see object 1997.0392.01, drift tube assembly.
label: Location
content: Currently not on view
setName: label: See more items in
content: Medicine and Science: Modern Physics
creditLine: label: Credit Line
content: Gift of John P. Blewett
dataSource: label: Data Source
content: National Museum of American History
identifier: label: ID Number
content: 1997.0392.02
label: accession number
content: 1997.0392
label: catalog number
content: 1997.0392.02
objectType: label: Object Name
content: tuning sphere
label: Object Name
content: Tuning sphere
label: Object Name
content: tuning ball
physicalDescription: label: Physical Description
content: copper (overall material)
label: Measurements
content: overall: 12.6 cm; 4 31/32 in