Vacuum tests of a beamline front-end mock-up at the Advanced Photon Sourcea)

Abstract

A mock-up has been constructed to test the functioning and performance of the Advanced Photon Source (APS) front ends. The mock-up consists of all components of the APS insertion-device beamline front end with a differential pumping system. Primary vacuum tests have been performed and compared with finite element vacuum calculations. Pressure distribution measurements using controlled leaks demonstrate a better than four decades of pressure difference between the two ends of the mock-up. The measured pressure profiles are consistent with results of finite element analyses of the system. The safety-control systems are also being tested. A closing time of ∼20 ms for the photon shutter and ∼7 ms for the fast closing valve have been obtained. Experiments on vacuum protection systems indicate that the front end is well protected in case of a vacuum breach.

Pressure wave propagation by gas expansion in a high vacuum tube

“…Figure 4 shows a schematic of the experimental setup 10 made to assess the calculated results. 7 However, the present calculated results will be useful as a criterion for large leak accidents because the real cases will have a somewhat longer propagation time. A shock wave is generated by pricking the diaphragm attached at the left end of the tube with a needle.…”

“…2 As to the propagation of pressure waves in a tube whose entrance is contracted by an orifice, as in the case of the transport tube for synchrotron radiation called the ''beamline,'' some investigations have been conducted. 6 Recently, vacuum tests of a beamline front-end mockup under controlled high vacuum conditions were conducted and compared with results obtained from a finite element analysis and a Monte Carlo simulation by Liu et al 7 They have shown that there was good agreement between measured and calculated pressure distributions along the mockup in the controlled small leak experiments. On the other hand, a gas flow model for shock wave problems in a tube, including changes in the cross-sectional area, has been available.…”