The focusing properties of the positron-capture solenoidal lens

Technical Report · Wed Jun 01 04:00:00 EDT 1988

DOI:https://doi.org/10.2172/378882· OSTI ID:378882

Yoon, M; Mavrogenes, G

This note concerns the focusing properties of the positron-capture solenoid. Such a solenoid will be placed before the entrance of the 450 MeV positron linear-accelerator injector in the APS. The 1.25 A, 40 ns electron beam is accelerated in the 200 MeV electron linac. This beam is then focused onto a 3 mm diameter spot at the 7 mm thick tungsten target. By the process of multiple nuclear-scattering the target generates the positron particles. These positrons, in general, can have a large diverging angle. In order to capture these rapidly diverging positrons, a relatively strong focusing lens is placed close to the converter. In this case a magnetic solenoidal lens has an advantage over the usual quadrupole lens because of its larger phase-space acceptance. In particular, the solenoidal lens is noted for its capability of controlling the spin direction of polarized ions. The authors first wrote down the expression for the magnetic field distribution on the axis for the solenoidal lens. From this expression they derive the expressions for the first- and second-order field distributions at any point in the region. They then calculate and compare the focal powers at various distances off the axis. Further, they calculate and include the third- and fourth-order components of the fields and compare them with the previous results. Finally, they briefly consider the particle trajectories through these fields and present the result in terms of the particle motion in phase space.

• Research Organization: Argonne National Lab., IL (United States)
• Sponsoring Organization: USDOE, Washington, DC (United States)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 378882
• Report Number(s): LS--122(ANL); ON: DE96015137
• Country of Publication: United States
• Language: English

Related Subjects

43 PARTICLE ACCELERATORS
ADVANCED PHOTON SOURCE
BEAM ACCEPTANCE
BEAM DYNAMICS
BEAM FOCUSING MAGNETS
BEAM OPTICS
COMPARATIVE EVALUATIONS
ELECTROMAGNETIC LENSES
FOCUSING
PERFORMANCE
POSITRON BEAMS
THEORETICAL DATA