There is a special reason for reviewing this book at this time: it is the 50th edition of a compendium that is known and used frequently in most chemical and physical laboratories in many parts of the world. Surely, a publication that has been published for 56 years, withstanding the vagaries of science in this century, must have had something to offer. There is another reason: while the book is a standard fixture in most chemical and physical laboratories, including those in medical centers, it is not as frequently seen in the laboratories of physician's offices (those either in solo or group practice). I believe that the Handbook can be useful in those laboratories. One of the reasons, among others, is that the various basic items of information it offers may be helpful in new tests, either physical or chemical, which are continuously being published. The basic information may relate

Handbook of Chemistry and Physics

The purpose of this article is to serve as a tutorial review on the subject of field emission and rf breakdown in high-gradient room-temperature accelerator structures and associated devices. The need to understand and control these two phenomena has become increasingly important because of the prospect of using high-gradient structures in future linear colliders. Electron field emission creates so-called dark current which parasitically absorbs rf energy, causes radiation, backgrounds, and possibly wakefields; it seems to be the precursor of rf breakdown, possibly in combination with local outgassing and plasma formation. In turn, rf breakdown limits the operation of accelerators and can cause irreversible damage to their physical structures. Research on these topics is interesting and challenging because it involves a mixture of disciplines such as surface physics, metallurgy, fabrication technologies, microwaves, beam dynamics and plasmas. This review consists of four parts: (1) field emission under dc, enhanced and rf conditions; (2) experimental set-ups; (3) prebreakdown stage--dark current and radiation; (4) experimental observations and analysis of rf breakdown. The review ends with conclusions and an outline of work that remains to be done.

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Field emission and RF breakdown in high gradient room temperature linac structures

We are exploring the physics and frequency-scaling of vacuum rf breakdowns at sub-THz frequencies. We present the experimental results of rf tests performed in metallic mm-wave accelerating structures. These experiments were carried out at the facility for advanced accelerator experimental tests (FACET) at the SLAC National Accelerator Laboratory. The rf fields were excited by the FACET ultrarelativistic electron beam. We compared the performances of metal structures made with copper and stainless steel. The rf frequency of the fundamental accelerating mode, propagating in the structures at the speed of light, varies from 115 to 140 GHz. The traveling wave structures are 0.1 m long and composed of 125 coupled cavities each. We determined the peak electric field and pulse length where the structures were not damaged by rf breakdowns. We calculated the electric and magnetic field correlated with the rf breakdowns using the FACET bunch parameters. The wakefields were calculated by a frequency domain method using periodic eigensolutions. Such a method takes into account wall losses and is applicable to a large variety of geometries. The maximum achieved accelerating gradient is $0.3\text{ }\text{ }\mathrm{GV}/\mathrm{m}$ with a peak surface electric field of $1.5\text{ }\text{ }\mathrm{GV}/\mathrm{m}$ and a pulse length of about 2.4 ns.

rf breakdown tests of mm-wave metallic accelerating structures

We present the design and a proof of principle experimental results of an optically controlled high-power RP pulse-compression system. In principle, the design should handle a few hundreds of megawatts of power at X-band. The system is based on the switched resonant delay-line theory [1]. It employs resonant delay lines as a means of storing RF energy. The coupling to the lines is optimized for maximum energy storage during the charging phase. To discharge the lines, a high-power microwave switch increases the coupling to the lines just before the start of the output pulse. The high-power microwave switch required for this system is realized using optical excitation of an electron-hole plasma layer on the surface of a pure silicon wafer. The switch is designed to operate in the TE/sub 01/ mode in a circular waveguide to avoid the edge effects present at the interface between the silicon wafer and the supporting waveguide; thus, enhancing its power handling capability.

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Active high-power RF pulse compression using optically switched resonant delay lines

The SwissFEL Injector Test Facility operated at the Paul Scherrer Institute between 2010 and 2014, serving as a pilot plant and testbed for the development and realization of SwissFEL, the X-ray Free-Electron Laser facility under construction at the same institute. The test facility consisted of a laser-driven rf electron gun followed by an S-band booster linac, a magnetic bunch compression chicane and a diagnostic section including a transverse deflecting rf cavity. It delivered electron bunches of up to 200 pC charge and up to 250 MeV beam energy at a repetition rate of 10 Hz. The measurements performed at the test facility not only demonstrated the beam parameters required to drive the first stage of an FEL facility, but also led to significant advances in instrumentation technologies, beam characterization methods and the generation, transport and compression of ultra-low-emittance beams. We give a comprehensive overview of the commissioning experience of the principal subsystems and the beam physics measurements performed during the operation of the test facility, including the results of the test of an in-vacuum undulator prototype generating radiation in the vacuum ultraviolet and optical range.

Commissioning experience and beam physics measurements at the SwissFEL Injector Test Facility

During the past several years, there has been tremendous progress on the development of the RF system and accelerating structures for a Next Linear Collider (NLC). Developments include high-power klystrons, RF pulse compression systems and damped/detuned accelerator structures to reduce wakefields. In order to integrate these separate development efforts into an actual X-band accelerator capable of accelerating the electron beams necessary for an NLC, we are building an NLC Test Accelerator (NLCTA). The goal of the NLCTA is to bring together all elements of the entire accelerating system by constructing and reliably operating an engineered model of a high-gradient linac suitable for the NLC. The NLCTA will serve as a testbed as the design of the NLC evolves. In addition to testing the RF acceleration system, the NLCTA is designed to address many questions related to the dynamics of the beam during acceleration. In this paper, we will report on the status of the design, component development, and construction of the NLC Test Accelerator. >

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The Next Linear Collider Test Accelerator

It is important to minimize power loss in the waveguide system connecting klystron, pulse-compressor, and accelerator in an X-Band NLC. However, existing designs of klystron output cavity circuits and accelerator input couplers utilize rectangular waveguide which has relatively high transmission loss. It is therefore necessary to convert to and from the low-loss mode in circular waveguide at each end of the system. A description is given of development work on high-power, high-vacuum 'flower-petal' transducers, which convert the TE/sub 10/ mode in rectangular guide to the TE/sub 01/ mode in circular guide. A three-port modification of the flower petal device, which can be used as either a power combiner at the klystron or a power divider at the accelerator is also described. >

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Flower-petal mode converter for NLC

Increasing the peak RF power available from X-band microwave tubes by means of RF pulse compression is envisioned as a way of achieving the few-hundred-megawatt power levels needed to drive a next-generation linear collider with 50-100 MW klystrons. SLED-II is a method of pulse compression similar in principal to the SLED method currently in use on the SLC and the LEP injector linac. It utilizes low-loss resonant delay lines in place of the storage cavities of the latter. This produces the added benefit of a flat-topped output pulse. At SLAC, we have designed and constructed a prototype SLED-II pulse-compression system which operates in the circular TE/sub 01/ mode. It includes a circular guide 3-dB coupler and other novel components. Low-power and initial high-power tests have been made, yielding a peak power multiplication of 4.8 at an efficiency of 40%. The system will be used in providing power for structure tests in the ASTA (Accelerator Structures Test Area) bunker. An upgraded second prototype will have improved efficiency and will serve as a model for the pulse compression system of the NLCTA (Next Linear Collider Test Accelerator). >

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High-power RF pulse compression with SLED-II at SLAC

An experiment to study the effects of pulsed heating in electromagnetic cavities will be performed. Pulsed heating is believed to be the limiting mechanism of high acceleration gradients at short wavelengths. A cylindrical cavity operated in the TE/sub 011/ mode at a frequency of 11.424 GHz will be used. A klystron will be used to supply a peak input power of 20 MW with a pulse length of 1.5 /spl mu/s. The temperature response of the cavity will be measured by a second waveguide designed to excite a TE/sub 012/ mode in the cavity with a low-power CW signal at a frequency of 17.8 GHz. The relevant theory of pulsed heating will be discussed and the results from cold-testing the structure will be presented.

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Experimental study of pulsed heating of electromagnetic cavities

A prototype of a muffin-tin accelerating structure operating at 32 times the SLAG frequency (2.856 GHz) was built for research in high gradient acceleration. A traveling-wave design with single input and output feeds was chosen for the prototype which was fabricated by wire electrodischarge machining. Features of the mechanical design for the prototype are described. Design improvements are presented including considerations of cooling and vacuum.

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A. Menegat

Papers

The Next Linear Collider Test Accelerator

Flower-petal mode converter for NLC

High-power RF pulse compression with SLED-II at SLAC

Experimental study of pulsed heating of electromagnetic cavities

Design and fabrication of a traveling-wave muffin-tin accelerating structure at 90 GHz