A Sheet-beam Klystron Paper Design

نویسنده

  • G. Caryotakis
چکیده

What may be the first detailed cold test and computer simulation analysis of a Double Sheet Beam Klystron (DSBK) was performed at SLAC. The device was conceptually designed mechanically, and evaluated electrically for beam formation, gain, stability and efficiency. It is believed that the DSBK can be built at a relatively low cost for a future NLC collider and can produce at least 150 MW at 11.4 GHz with PPM focusing. Voltage and current are 450 kV and 640 A, respectively. The Sheet Beam Klystron (SBK) is a device that has been considered as a microwave source for at least 60 years, but has never been fully designed or constructed. It was first proposed by Kovalenko in Russia in 1938 and revisited repeatedly over the years in the USSR, France and the US. The fact that no serious attempt was ever made to build and test an SBK can probably be attributed to the existence of alternatives and to perceived electrical and mechanical difficulties. The principal electrical difficulties have been the large drift tube and overmoded cavities that the SBK requires. Also, designers have been concerned with the possibility that the sheet beam might be unstable suffering from diocotron break-up, or be difficult to contain laterally at the edges. Mechanical issues centered mostly at the gun, and the thermal design of a large cathode/heater package. Certainly, the construction of sheet-beam guns is beyond the capabilities of most universities and national laboratories. Industry, for the most part, has not taken on the SBK design problem, simply because other klystron types could serve existing requirements, or could be easily developed. The chief virtue of the SBK is that its large lateral dimensions permit high power to be attained with low current densities in the cathode, and low power concentration in the cavities. This is the same advantage that multiple beam klystrons have over single-beam klystrons. The difference is that an SBK can be made with a fraction of the parts an MBK requires, or for that matter, that are normally used in an ordinary klystron. At SLAC, the logistics of the Next Linear Collider (NLC) initially required several thousand 75-MW X-band klystrons for the 500 GeV versions of the machine. Gradually, as these tubes were built, put to use, and accumulated hours, confidence in their performance led to increases in the pulse length and the ratio of pulse compression. Today, the baseline NLC klystron has a pulse length of approximately 3 microseconds and the number of PPM-focused klystrons is approximately 1600. Obviously, this is still a large number of fairly complicated tubes. A klystron with twice the output would be very desirable, especially if a 1-TeV NLC were to be considered. However, 150 MW peak and a 50 kW average power at 11.4 GHz is uncomfortably high with a single beam and an output circuit with a one-centimeter bore. This is what motivated us to look very seriously into the SBK. Through a process of parameter trade-offs, the design that has emerged employs two beams, each with an aspect ratio of 10:1 and perveance of 1.1 x 10 -6 (0.11 micropervs per square). These are conservative numbers, and they are, in part, dictated by the necessity to use periodic focusing and to place magnets and polepieces at some distance from the beams in order to simplify the mechanical design and allow water-cooling in the space between the circuit and the magnet stack. SLAC-PUB-8967 5th Modulator-Klystron Workshop for Future Linear Colliders (MDK-2001) CERN, PS Division, Geneva, 26-27 April 2001 Work supported by the Department of Energy contract DE-AC03-76SF00515. As a matter of fact, mechanical considerations formed the basis for the overall design of this DSBK (Double Sheet Beam Klystron). Referring to Figs. 1 and 2, it can be seen that the cavities, drift tunnels and collectors are fabricated on numerically controlled machines out of four (4) slabs of copper. The two klystrons making up the DSBK share the same vacuum plenum at the double gun, but are otherwise separate mechanically and electrically. The two halves of each klystron are separated by a fraction of a millimeter so that cavities and drift tubes can be pumped from vacuum manifolds running along the entire length of the rf sections and the collectors. This is possible because the TM modes in the cavities do not have rf currents crossing the surface where the two halves are separated. (The guns are shown gridded because the picture was drawn for a different version of the DSBK).

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Development of a 10 Mw Sheet Beam Klystron for the Ilc*

SLAC is developing a 10 MW, 5 Hz, 1.6 ms, L-band (1.3 GHz) Sheet-Beam Klystron as a less expensive and more compact alternative to the ILC baseline MultipleBeam Klystron. The Klystron is intended as a plugcompatible device of the same beam current and operating voltage as existing Multiple-Beam Klystrons. At this time, a beam tester has been constructed and currently is in test. The beam tester...

متن کامل

Design of a Wiggler - Focused , Sheet Beam X Band Klystron

An X band klystron using a sheet beam and wiggler focusing was simulated using the 2 + t dimensional particle in cell code MASK.’ Simulation of the rf cavities was by means of the port approximation used in modell ing of standard klystrons.2 The wigglers, which would need permanent magnets to achieve the required field strengths, were modelled using an idealized analytic expression with an expo...

متن کامل

The Design and Performance of 150-MW S-Band Wystrons

As part of an international collaboration, the Stanford Linear Accelerator Center (SLAC) klystron group has designed, fabricated and tested a 60 Hz, 3 W, 150 MW klystron built for Deutsches Elektronen Synchrotron (DESY). A test diode with a 535 kV, 700 A electron beam was constructed to verify the gun operation. The first klystron was built and successfully met design specifications. This paper...

متن کامل

Operational Experience with Slac Energy Upgrade ’

To produce energies of over 50 GeV for SLC, all klystron stations on the accelerator ue being upgraded to produce 250 MeV energy contribution per station. This involves installii new, higher power, longer pulse klystrons, upgrading klystron modulators to provide these higher voltage, longer klystron beam pulses, and a new interlock and protection system.’ A new VAX based diagnostic system inclu...

متن کامل

Periodic Permanent Magnet Development for Linear Collider X-band Klystrons

* This work is supported by the Department of Energy under Contract DE-AC03-76SF00515 Abstract The Stanford Linear Accelerator Center (SLAC) klystron group is currently designing, fabricating and testing 11.424 GHz klystrons with peak output powers from 50 to 75 MW at 1 to 2 μs rf pulsewidths as part of an effort to realize components necessary for the construction of the Next Linear Collider (...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2001