Resistive wall heating due to image current on the beam chamber for a superconducting undulator.

Kim, S. H. (Accelerator Systems Division (APS))

关键词: ALLOYS;    ALUMINIUM;    BEAM CURRENTS;    COPPER;    CRYOGENICS;    CURRENT DENSITY;    ELECTRON BEAMS;    HARMONICS;    HEATING;    SKIN EFFECT;    STORAGE RINGS;    WIGGLER MAGNETS;   

DOI  :  10.2172/1039517
RP-ID  :  ANL/APS/LS-329
PID  :  OSTI ID: 1039517
Others  :  TRN: US1202262

学科分类：核物理和高能物理

美国|英语

来源: SciTech Connect

【 摘 要 】

The image-current heating on the resistive beam chamber of a superconducting undulator (SCU) was calculated based on the normal and anomalous skin effects. Using the bulk resistivity of copper for the beam chamber, the heat loads were calculated for the residual resistivity ratios (RRRs) of unity at room temperature to 100 K at a cryogenic temperature as the reference. Then, using the resistivity of the specific aluminum alloy 6053-T5, which will be used for the SCU beam chamber, the heat loads were calculated. An electron beam stored in a storage ring induces an image current on the inner conducting wall, mainly within a skin depth, of the beam chamber. The image current, with opposite charge to the electron beam, travels along the chamber wall in the same direction as the electron beam. The average current in the storage ring consists of a number of bunches. When the pattern of the bunched beam is repeated according to the rf frequency, the beam current may be expressed in terms of a Fourier series. The time structure of the image current is assumed to be the same as that of the beam current. For a given resistivity of the chamber inner wall, the application ofthe normal or anomalous skin effect will depend on the harmonic numbers of the Fourier series of the beam current and the temperature of the chamber. For a round beam chamber with a ratius r, much larger than the beam size, one can assume that the image current density as well as the density square, may be uniform around the perimeter 2{pi}r. For the SCU beam chamber, which has a relatively narrow vertical gap compared to the width, the effective perimeter was estimated since the heat load should be proportional to the inverse of the perimeter.