Constant-current charging supplies for the Advanced Photon Source (APS) linear accelerator modulators

Abstract

The APS [1,2] linac beam energy must be stable to within 21% to match the energy acceptance of the positron accumulator ring. The klystron pulse modulators [3,4] must therefore provide a pulse-to-pulse repeatability of 0.1% in order for the beam to have the required energy stability. The modulators have had difficulty achieving the necessary repeatability since the pulse forming network (PFN) charging scheme does not include a deQing circuit. Several of the major charging circuit components are also less reliable than desired. In order to increase operating reliability and to improve pulse-to-pulse stability, it is planned to replace the high voltage power supplies in all modulators with constantcurrent power supplies. A new modulator charging supply that contains two EM1 [SI series 303 constant-current power supplies was constructed. Each of these EM1 supplies delivers 1.5 A at up to 40 kV. One supply is sufficient for linac operation at up to 15 Hz, and two supplies in parallel enable linac operation at the nominal rf repetition rate of 60 Hz. This paper discusses test results from the new modulator, and ais0 describes the existing modulators and their performance limitations.

Klystron-modulator system performance for the Advanced Photon Source linear accelerator

“…The detailed performance test results are well documented in Ref. [5]. The redesigned circuit schematic of the APS modulator is shown in Fig.…”

“…Normal experimental projects during user beam are the LEUTL-FEL studies [3], which require highly reliable linac performance with machine availability as high as possible. Since the completion of the APS linac in 1994, there have been a number of upgrade efforts to improve the system reliability and availability, such as installation of a precision temperature control system, a low-level rf system, a pulse modulator system [4,5], the bunch compressor, and a high-power waveguide switch network installation [6].…”

The advanced photon source linac modulators PSpice simulation and upgrade

“…rate. The modulator has a fairly standard design and has been presented at various particle accelerator conferences [1,2].…”

“…rate. The modulator has a fairly standard design and has been presented at various particle accelerator conferences [1,2].The APS linac modulators provide DC pulses to Thales 35/45-MW klystrons. The modulators are pulse forming network (PFN)-type pulsers with EMI 40-kV switch-mode charging supplies.…”