The longitudinal coupling impedance of a slot on the SSC collider liner

Technical Report · Tue Dec 01 04:00:00 EST 1992

OSTI ID:10133063

Thiagarajan, V

The location of a liner inside the Collider beam tube is under study at the Superconducting Super Collider Laboratory. The purpose of the liner is two-fold. It will be at a temperature higher than that of the beam tube and will help remove the synchrotron radiation energy from the 20-TeV proton beam, thus reducing the load on the cryogenic system. The liner is also designed to,enhance the vacuum toward higher beam currents and luminosities. A definite distribution of holes (or slots) with the required pumping area needs to be located on the surface of the liner to maintain the vacuum. On the negative side, there will be diffracted wake fields following the beam fields incident on the pumping holes. These wake fields may attenuate with distance or propagate, depending on the frequency. They will cause longitudinal and transverse forces on the following bunches of protons and may result in coherent multi-bunch instabilities, as well as cause bunch lengthening and emittance growth. The effect of the wake fields may be expressed through the longitudinal and transverse coupling impedances, which are defined proportional to the corresponding forces integrated through distance, per unit charge. This report describes a method to evaluate the longitudinal coupling impedance of slots or holes of given dimensions on the liner, as a function of the frequency in the range 0 to approximately 100 GHz, in order to facilitate optimum choice of slots or holes on the liner.

• Research Organization: Superconducting Super Collider Lab., Dallas, TX (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: AC35-89ER40486
• OSTI ID: 10133063
• Report Number(s): SSCL--615; ON: DE93009438
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
430200
430303
BEAM BUNCHING
BEAM DYNAMICS, FIELD CALCULATIONS, AND ION OPTICS
BEAM EMITTANCE
BOUNDARY CONDITIONS
ELECTROMAGNETIC FIELDS
EXPERIMENTAL FACILITIES AND EQUIPMENT
IMPEDANCE
LINERS
NORMAL-MODE ANALYSIS
SUPERCONDUCTING SUPER COLLIDER
SYNCHROTRON RADIATION
WAVEGUIDES