RF system for the NSLS coherent infrared radiation source

Abstract

S u b A t t e d t o the 1995 P a r t i c l e A c c e l e r a t o r C o n f e r e n c e , 'Dallas, Texas, 'May 1-5, 1995. is being considered for a coherent synchrotron radiation source. The existing 211 MHz warm cavity will be replaced with a 5-cell2856 MHz superconducting RF cavity, driven by a series of 2 kW klystrons. The RF system will provide a total VRF of 1.5 MV to produce OL = 0.3 mm electron bunches at an energy of 150 MeV.Superconducting technology significantly reduces the required space and power needed to achieve the higher voltage. It is the purpose of this paper to describe the superconducting RF system and cavity, power requirements, and cavity design parameters such as input coupling, Quality Factor, and Higher Order Modes. II. INTRODUCTIONThe XLS Phase I storage ring is a compact racetrack-shaped ring at the National Synchrotron Light Source of Brookhaven National Laboratory. Using a warm 211 MHz RF cavity, currents of up to 0.75 A in 6 bunches have previously been stored at energies ranging from 120 to 200 MeV. Installation of a 5-cell2856 MHz superconducting cavity will provide an accelerating voltage of 1.5 MV for an average current of up to 5 mA, and create a source of coherent synchrotron radiation with 0.3 mm bunches at an energy of 150 MeV [l]. In order to accommodate the cavity, cryostat and helium vessel, and other associated hardware, the circumference of the ring can be increased to -9.66 from the present 8.5 m by adding a short straight section on both sides, keeping modification costs to a minimum. A partial list of the ring and RF parameters is presented in Table 1. capital cost of a closed cycle system [ Figure I]. Initially, the cryostat will be filled with normal helium; the 2' K operating temperature will be achieved through cryo-pumping. Although it is rather large, the "top-filled" cryostat is relatively easy to operate and is capable of supplying enough helium for 8 continuous hours of operation. The main difficulties foreseen are with the assembly sequences. The RF cavity will have protective windows and valves as safeguards after cleaning. The cavity design [ Figure 21 is being adapted and scaled from that currently in use at Cornell and CEBAF [2,3,4], including the input waveguide and the HOM couplers. There are 5 elliptical cells operating in the ~t mode. Scaling of CEBAF results to a 2856 MHz cavity indicates that a gradient of 8.9 MVJm is achievable. With an active length of 0.262 m, a peak cavity voltage, Vu, of 2.3 MV can be reached, which is 50% greater than specified. The order of magnitude of the unloaded quality factor Qo, is approximately lo9. A. Input CouplingAs in the CEBAF design, RF power is propagated in the TElo p = PRAD 1 P a v 0.2 III. CRYOGENICSmode through a rectangular waveguide. A hole in the broad of the waveguide that is aligned with the beam tube, The system will use a helium reservoir, operating at 2 O K, rather than circulating refrigeration because of the high initial

Generic study on the design and operation of high power targets

“…Energy deposition in the target depends on beam energy, beam profile, and target geometry [14]. Cooling systems are designed to evacuate the heat produced in the target due to beam impact, plus any heat produced as a result of the decay process of radioactive target nuclei.…”

Millimeter wave coherent synchrotron radiation in a compact electron storage ring

“…The properties of the 2856 MHz superconducting RF system to be used in the XLS ring are given in Table 5. A more complete discussion of the RF cavity can be found in reference [6]. …”