• F. Wang, C. Adolphsen
  SLAC, Menlo Park, California

Funding: Work supported by the DOE under contract DE-AC02-76SF00515

An L-band (1.3 GHz), normal-conducting, five-cell, standing-wave cavity that was built as a prototype capture accelerator for the ILC is being high-power processed at SLAC. The goal is to demonstrate stable operation at 15 MV/m with 1 msec, 5 Hz pulses and the cavity immersed in a 0.5 T solenoidal magnetic field. This paper summarizes the performance that was ultimately achieved and describes a novel analysis of the modal content of the stored energy in the cavity after a breakdown to determine on which iris it occurred.

• C. Adolphsen, G.B. Bowden, V.A. Dolgashev, L. Laurent, S.G. Tantawi, F. Wang, J.W. Wang
  SLAC, Menlo Park, California
• S. Döbert, A. Grudiev, G. Riddone, W. Wuensch, R. Zennaro
  CERN, Geneva
• Y. Higashi, T. Higo
  KEK, Ibaraki

Funding: Work supported by the DOE under contract DE-AC02-76SF00515

As part of a SLAC-CERN-KEK collaboration on high gradient X-band structure research, several prototype structures for the CLIC linear collider study have been tested using two of the high power (300 MW) X-band rf stations in the NLCTA facility at SLAC. These structures differ in terms of their manufacturing (brazed disks and clamped quadrants), gradient profile (amount by which the gradient increases along the structure which optimizes efficiency and maximizes sustainable gradient) and HOM damping (use of slots or waveguides to rapidly dissipate dipole mode energy). The CLIC goal in the next few years is to demonstrate the feasibility of a CLIC-ready baseline design and to investigate alternatives which could bring even higher efficiency. This paper summarizes the high gradient test results from the NLCTA in support of this effort.

• C. Adolphsen, A.A. Haase, D. Kiehl, C.D. Nantista, T.N. Nieland, J. Tice, F. Wang
  SLAC, Menlo Park, California

Funding: Work supported by the DOE under contract DE-AC02-76SF00515

A new facility to clean, assemble, bake and rf process TTF3-style power couplers has been completed and is in operation at SLAC. This facility includes a class-10 cleanroom, bake station and an L-band source capable of producing up to 4 MW pulses. This paper describes the facility, test results from processing pairs of couplers that will be used in cryomodules at FNAL, and efforts to simplify the design and manufacturing of the couplers for large scale use at ILC. Also, tests of the couplers to explore their power limits for use in an FNAL superconducting proton linac are presented.

• C.D. Nantista, C. Adolphsen
  SLAC, Menlo Park, California

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515.

We present a concept for powering the main linacs of the International Linear Collider (ILC) by delivering high power RF from the surface via overmoded, low-loss waveguides at widely spaced intervals. The baseline design employs a two-tunnel layout, with klystrons and modulators evenly distributed along a service tunnel running parallel to the accelerator tunnel. This new idea eliminates the need for the service tunnel. It also brings most of the warm heat load to the surface, dramatically reducing the tunnel water cooling and HVAC requirements. In the envisioned configuration, groups of 70 klystrons and modulators are clustered in surface buildings every 2.4 km. Their outputs are combined into two half-meter diameter circular TE01 mode evacuated waveguides. These are directed via special bends through a deep shaft and along the tunnel, one upstream and one downstream. Each feeds approximately 1.2 km of linac with power tapped off in 10 MW portions at 38 m intervals. The power is extracted through a novel coaxial tapoff (CATO), after which the local distribution is as it would be from a klystron. This tapoff design is also employed in reverse for the initial combining.

• S. Pei, C. Adolphsen
  SLAC, Menlo Park, California
• J. Carwardine
  ANL, Argonne
• N.J. Walker
  DESY, Hamburg

Funding: *Work supported by the DOE under contract DE-AC02-76SF00515

The FLASH L-Band superconducting (SC) accelerator facility at DESY has a LLRF system that is similar to that envisioned for ILC. This system has extensive monitoring capability and was used to gather performance data relevant to ILC. In particular, waveform data were recorded with beam off for three, 8-cavity cryomodules to evaluate the input rf stability, perturbations to the SC cavity frequencies and the rf overhead required to achieve constant gradient during the 800 μs pulses. In this paper, we discuss the measurements made in September 2008 and the data analysis procedures, and present key findings on the pulse-to-pulse input rf and cavity field stability.

• K.L.F. Bane, C. Adolphsen, A. Jensen, Z. Li, G.V. Stupakov
  SLAC, Menlo Park, California

Funding: Work supported by the U.S. Department of Energy under contract DE-AC02-76SF00515.

An L-band (1.3 GHz) sheet beam klystron that will nominally produce 10 MW, 1.6 ms pulses is being developed at SLAC for the ILC program. In recent particle-in-cell transport simulations of the 115 kV DC beam through the klystron buncher section without rf drive, a hose-type instability has been observed that is the result of beam noise excitation of transverse modes trapped between the rf cells. In this paper we describe analytical calculations and numerical simulations that were done to study the nature of this instability and explore the required mode damping and changes in the beam focusing to suppress it.

• R.S. Larsen, C. Adolphsen, D.J. McCormick, W.C. Ross, Z.M. Szalata
  SLAC, Menlo Park, California
• R.W. Downing
  R.W. Downing Inc., Tucson

Funding: US Department of Energy Contract DE AC03 76SF00515.

The ILC R&D electronics program at SLAC includes development of key technologies aimed at improving reliability and availability and reducing cost. This paper discusses the development of high availability interlocks and controls for the L-Band high power RF stations. A new Fast Fault Finder (F3) VME module has been developed to process both slow interlocks using FPGA logic to detect the interlock trip excursions. This combination eliminates the need for separate PLC control of slow interlocks with modules chained together to accommodate as many inputs as needed. Next a high availability platform demonstration will port the F3’s via a specially designed VME adapter module into the new industry standard ATCA[1] crate (shelf). This high-availability platform features an Intelligent Platform Management (IPMI) system to control and monitor the health of the entire system, provide redundancy as needed for the application, and demonstrate auto-failover and hot-swap to minimize MTTR. The goal is to demonstrate “five nines” (0.99999) system availability at the shelf level. A new international initiative, the xTCA for Physics Standards Working Group, will be briefly mentioned.

[1] Advanced Telecom Computing Architecture