Single Klystron Research Articles

Design and realization of a single klystron-based radio frequency system for a radio frequency quadrupole and a drift tube linac

This work describes the design and realization of a radio frequency (RF) system with a single klystron to power two conjunct independent cavities, namely, an RF quadrupole (RFQ) and a drift tube linac (DTL). In contrast with a two-klystron scheme, an RF system that adopts a single-klystron scheme for two accelerating cavities exhibits simpler configuration, smaller occupation area, and lower cost. However, the low intrinsic flexibility of the single-klystron scheme needs to be compensated by independent adjustment of RF field phases and amplitudes inside the two cavities. A proposed RF system design based on the single-klystron scheme includes a 4.77 dB power divider, an adjustable power attenuator, and a phase shifter. The power attenuator and phase shifter are set in different branches of the RF power transmission line. This design is used to power an RFQ and a downstream DTL in the Compact Pulsed Hadron Source (CPHS) at Tsinghua University. During commissioning, the amplitudes inside the RFQ and DTL and the relative phase difference between them can be adjusted independently. The 13 MeV proton beam commissioning result verifies the design parameters and effectiveness of the single-klystron-based RF system. A proton beam energy of 12.92 MeV and a beam peak current of 41.2 mA at the exit of DTL were achieved, and the beam transmission from the entrance of RFQ to the exit of DTL reached 88.6%.

Microphonics Suppression In Ariel Acm1 Cry- Omodule

Now 30 MeV stage of the ARIEL (The Advanced Rare Isotope Laboratory) e-Linac is under commissioning which includes an injector cryomodule (ICM) and the first accelerator cryomodule (ACM1). The two ACM1 cavities are driven by a single klystron with vector-sum control and running in CW mode. During the commissioning, the ACM1 cavities gradient and stability were limited by a ponderomotive effect [1-4]. Acoustic noise from the environment including vibration sources from water- and air-cooling systems, cryogenic system and vacuum system have been identified. In this paper, the progress of the microphonics suppression of ACM1 is presented.

A new technique for RF distribution

For independent phase and amplitude control, RF cavities are often driven by one power source per cavity. In many cases it would be advantageous in terms of cost to instead use one higher power source for many cavities. Vector modulators have been developed, which, when used with a single source provide for the independent phase and amplitude control which would have been otherwise lost. The key components of these vector modulators are a novel type of phase shifter — adjustable fast phase shifters with perpendicularly biased garnets. The vector modulators have been constructed and used with a single klystron in a 3.4 MeV test linac to successfully accelerate proton beam.

Design of RF Power System for CPHS

Abstract The Compact Pulsed Hadron Source (CPHS) system has been proposed and designed by the Department of Engineering Physics of Tsinghua University in Beijing, China. It consists of an accelerator front-end—a highintensity ion source, a 3 MeV radiofrequency quadrupole linac (RFQ), and a 13 MeV drift-tube linac (DTL), a neutron target station, and some experimental stations. In design of our RF power supply, both RFQ and DTL share a single klystron which is capable of 2.5 MW peak RF power and a 3.33% duty factor. The 325 MHz klystron contains a modulating anode and has a 100 kW average output power. Portions of the RF power system, such as pulsed high voltage power supply, modulator, crowbar protection and RF power transmission are all presented in details in this paper.

RF Characteristics of Four Independent DTL Tanks Driven by a Single Klystron

RF Characteristics of Four Independent DTL Tanks Driven by a Single Klystron

Production of beat waves using S-band klystron amplifier

A method of producing beat waves by a single klystron amplifier is introduced in this paper. The experimental results have been obtained that the main frequency of the beat wave is in S-band, the beat frequency ranges from 10 to 120MHz, the peak power of the pulsed beat wave is 1MW, and the maximal repetitive frequency is 500pps. This method has been successfully used in certain electrical system high-power microwave vulnerability effect experiments.

Development of an asymmetric power divider for a high-power RF distribution system

We have developed a radio-frequency (RF) power divider that is used for an RF distribution system in high-energy electron storage rings. This power divider has four waveguide ports, and it can split a high RF power by a ratio of 1:2 at an operating frequency of about 508.6 MHz. Since other properties are very similar to those of a magic-T it is very suitable for accelerator applications. By combining this device with a conventional magic-T, one can design an RF distribution system in which three cavities are driven by a single klystron. The design procedure of the power divider, a low-power measurement, and a high-power test result are presented.

Multiple-quantum electron-electron double resonance

Continuous wave electron-electron double resonance involves the irradiation of one line in an EPR spectrum with an intense “pumping” microwave source and the observation of the effect of that irradiation on another line of the spectrum using a weaker “observing” microwave source. In fluid samples, three ELDOR mechanisms that can be responsible for the transfer of saturation from the pumped transition to the observed transition have been identified. These are Heisenberg exchange between colliding paramagnetic molecules ( 1)) nuclear relaxation induced by rotational modulation of electron nuclear dipolar interaction ( 1)) and, in samples undergoing very slow rotational diffusion, spectral diffusion because of rotational diffusion (2, 3). The ELDOR technique and also relevant theory were introduced in Ref. (1). ELDOR is the subject of a monograph (4) and has been recently reviewed (5). The longitudinal detection of electron paramagnetic resonance involves the irradiation of a single homogeneous line by two closely spaced equally intense microwave frequencies. It was shown by workers at the University of Pisa (6, 7) that under this irradiation multiquantum transitions are induced. The M, component of magnetization oscillates at the difference between the microwave frequencies as well as at multiples of the difference. These workers directly detected these Zeeman oscillations with a pick-up coil oriented along B,,. In this paper, we report the transfer of Zeeman oscillations as induced by two closely spaced microwave frequencies that irradiate one EPR transition to another EPR transition because of liquid-phase Heisenberg exchange. Thus, three CW microwave frequencies are incident on the spin system: two closely spaced frequencies (nominally 10 kHz apart at X band) that serve together to pump a transition and a weaker third frequency used to observe another transition. All frequencies are derived from a single klystron by use of a single sideband mixer (SSM) in an unusual configuration (Fig. 1). The two inputs of the SSM are supplied by the two outputs of the Hewlett-Packard 3326A two-channel synthesizer set to two

A compact and economical injector for free electron lasers

The various successful demonstrations of FEL oscillation have verified the theory and established practical design techniques. FELs should now move into the realm of user devices, whether scientific or commercial. Potential users will be looking for sources of electron beams which are both compact in size and economical to manufacture. The present paper suggests a type of recirculating linac which could give energies in the range of 50 to several hundred MeV using a single klystron, whilst maintaining all the desirable properties given to the beam by the preinjection system. The latter could incorporate, for instance, the proposals of Stanford (HEPL) or Los Alamos for the production of very low emittance, low energy spread beams with high peak currents. The klystron would essentially have a long macropulse (∼ 100 μs) and could be either L-band or S-band, the former having some advantages at high peak currents. In principle the device could be cw, using either conventional or superconducting technology, although this would be more costly. The proposed accelerator might well be the best means of achieving a VUV FEL, if sufficiently low emittance electron beams can be produced.

The Design and Performance of a 150-MW Klystron at S Band

Design considerations and performance characteristics of a 150-MW pulsed klystron amplifier at S band are described. One of the main problems encountered in generating such high power at microwave frequencies is the extremely high-voltage gradients developed across the output gap of the klystron which may cause RF breakdown. A double-gap 2π-mode output cavity is used successfully in the present case to generate a peak output power of 150 MW at a frequency of 2870 MHz with an efficiency of 51 percent, saturation gain of 59.3 dB, and a pulsewidth of 1 μs. A reduction in gap voltage of at least 25 percent as compared to a similar klystron with a conventional single-gap output cavity at the same voltage and at their respective maximum efficiency points is theoretically predicted. Examination of the gaps after an extended period of operation shows that they are smooth and without signs of erosion, indicating that the fields were uniform and not excessive. Extrapolating from the gradient which exists in this present tube, it appears feasible to generate still higher powers (of the order of 700 MW) efficiently with a single klystron at S band with a pulsewidth of 1 μs, if the need arises.

A Racetrack Microtron RF System

The rf system for the National Bureau of Standards (NBS)/Los Alamos cw racetrack microtron is described. The low-power portion consists of five 75-W amplifiers that drive two input ports in each of two chopper deflection cavities and one port in the prebuncher cavity. A single 500-kW klystron drives four separate 2380-MHz cavity sections: the two main accelerator sections, a capture section, and a preaccelerator section. The phases and amplitudes in all cavities are controlled by electronic or electromechanical controls. The 1-MW klystron power supply and crowbar system were purchased as a unit; several modifications are described that improve power-supply performance. The entire rf system has been tested and shipped to the NBS, and the chopper-buncher system has been operated with beam at the NBS.

An Optimized Design for PIGMI

PIGMI (Pion Generator for Medical Irradiations) is a compact linear proton accelerator design, optimized for pion production and cancer treatment use in a hospital environment. Technology developed during a four-year PIGMI Prototype experimental program allows the design of smaller, less expensive, and more reliable proton linacs. A new type of low-energy accelerating structure, the radio-frequency quadrupole (RFQ) has been tested; it produces an exceptionally good-quality beam and allows the use of a simple 30-kV injector. Average axial electric-field gradients of over 9 MV/m have been demonstrated in a drift-tube linac (DTL) structure. Experimental work is underway to test the disk-and-washer (DAW) structure, another new type of accelerating structure for use in the high-energy coupled-cavity linac (CCL). Sufficient experimental and developmental progress has been made to closely define an actual PIGMI. It will consist of a 30-kV injector, an RFQ linac to a proton energy of 2.5 MeV, a DTL linac to 125 MeV, and a CCL linac to the final energy of 650 MeV. The total length of the accelerator is 133 meters. The RFQ and DTL will be driven by a single 440-MHz klystron; the CCL will be driven by six 1320-MHz klystrons. The peak beam current is 28 mA. The beam pulse length is 60 ps ?s at a 60-Hz repetition rate, resulting in a 100-?A average beam current. The total cost of the accelerator is estimated to be ~$10 million.

Application of a serrodyne single sideband generator in a single klystron superheterodyne epr spectrometer

It is demonstrated experimentally that a serrodyne single sideband generator is a simple technique for providing the microwave frequency translation required in single klystron superheterodyne epr spectrometers. The frequency can be translated up to 100 kHz by sawtooth phase modulation using a microwave ferrite phase modulator. The advantages of the serrodyne method of frequency translation are that: (i) it is relatively efficient since the sum of the insertion loss and the frequency conversion loss is of the order of 2.2 dB at 50 kHz; (ii) no additional microwave components are required to obtain approximately 17 dB suppression of the carrier and unwanted sidebands; (iii) the output frequency and amplitude are insensitive to noise in the driving circuitry to the ferrite phase modulator; (iv) ferrite phase modulators are nonmicrophonic; (v) commercial ferrite phase modulators with a bandwidth of about 5% are available in the waveguide frequency bands from 8 to 140 GHz. It is found that the sensitivity of a 35 GHz homodyne epr spectrometer using a 50 kHz intermediate frequency and 400 Hz magnetic field modulation exceeds that obtained using only the 400 Hz magnetic field modulation, but with the phase modulator inserted but inoperative, by a factor of the order of (8+or-1). The theoretical increase in sensitivity is a factor of 11, assuming that 1/f noise is the dominant noise spectrum component of the microwave point-contact diodes (1N53BM) over this frequency range and the serrodyne is 100% efficient.

Long-Pulse Radio Frequency Separator Test Facility

This paper discusses a long-pulse, line-type modulator facility which has been built to operate either one or two SLAC-type klystrons for long-pulse RF particle separator studies. The modulator is capable of driving two klystrons to a peak beam power of 80 MW, 250 kW average, for 50μs pulses or one klystron to a peak beam power of 40 MW, 125 kW average. The modulator has two 25 μs pulse-forming networks which can be operated individually to drive a single klystron or in parallel to drive two klystrons from a common pulse transformer. In addition, test results for long-pulse operation of the SLAC-type klystron are presented.

A 9-GHz, SINGLE-KLYSTRON, EPR SPECTROMETER USING SUPERHETERODYNE DEMODULATION

A 9-GHz electron paramagnetic resonance (EPR) spectrometer, which features superheterodyne demodulation using a single klystron as the source of both the sample cavity and local oscillator (LO) power, is described. It uses a reflection cavity as part of a balanced bridge and operates in the absorption mode. The LO power is derived from the microwave carrier power source by a ferrite single side-band generator driven at a very low intermediate frequency (IF) 0(103–106) Hz. This spectrometer uses triple synchronous demodulation at the microwave, intermediate, and field modulation frequencies to overcome the instability usually associated with superheterodyne instrumentation. The sensitivity of the resulting demodulation system has a stability that is essentially independent of fluctuations in the degree of bridge balance and the instantaneous sample cavity resonant frequency, provided that the microwave power source is simultaneously phase-locked to a high stability, MHz crystal oscillator and to the instantaneous resonant frequency of the sample cavity. The sensitivity has been found to remain within 5% of a constant value for periods in excess of 30 days. No readjustments were necessary during this period because of the system stability inherent in this design. The environmental temperature of the spectrometer was maintained at 20 ± 2 °C. Experimental details are given and the results of a sensitivity study are presented graphically.

Hardpoint Demonstration Array Radar

The project HAPDAR (HArd Point Demonstration Array Radar) is a part of Project Defender, sponsored by the Advanced Research Projects Agency, Department of Defense, under ARPA Order Number 516 and contracted through the Army Missile Command. An attractive practical phased array radar system design is described in this paper. The HAPDAR radar is a multimode multifunction system capable of electronic scanning a pencil beam in two dimensions. The principal design feature is the TACOL (Thinned Aperture Computed Lens) approach to the antenna design. The lens is a passive array capable of collimating the beam and steering it in the desired direction. A single klystron transmitted illuminates the lens and a standard monopulse feed is used to extract angular errors. The design principles of TACOL are discussed and a complete description of the radar is presented.

A simple sensitive X-band superheterodyne spectrometer for electron spin resonance measurements

A single klystron superheterodyne X-band electron spin resonance spectrometer was constructed for sensitive measurements in a wide power region, 0.4 μw-4 mw. A 30 Mc/s modulation system was used to provide both the local oscillator power and to phase-lock the klystron frequency to the sample cavity.

The reflex klystron as a regenerative mixer

A simple receiver using a single reflex klystron as a mixer and local oscillator is described. Experimental data show typical performance, and a theory based on reflex-klystron and transmission-line theory is proposed which explains the observed behavior. The S- and X-band tangential sensitivities are about 15 db better than can be realized with a low-level crystal video detector and it is thought that this figure may be exceeded at the higher microwave frequencies where crystal sensitivity is relatively poor.

Measurement of Atmospheric Attenuation at Millimeter Wavelengths

A frequency-modulation radar technique especially suited to measurement of atmospheric attenuation at millimeter wavelengths is described. This two-way transmission method employs a single klystron, a single antenna and a set of spaced corner reflectors whose relative reflecting properties are known. Since the method does not depend on measurements of absolute antenna gains and power levels, absorption data can be obtained more readily and with greater accuracy than by the usual one-way transmission methods. Application of the method is demonstrated by measurements in the 5-mm to 6-mm wave band. The results have made it possible to assign an accurate value for the line-breadth constant of oxygen at atmospheric pressure; the constant appropriate to the measurements lies between 600 and 800 MCS per atmosphere.