• M.E. Conde, S.P. Antipov, W. Gai, F. Gao, R. Konecny, W. Liu, J.G. Power, Z.M. Yusof
  ANL, Argonne
• C.-J. Jing
  Euclid TechLabs, LLC, Solon, Ohio

Funding: Work supported by the U.S. Department of Energy under contract No. DE-AC02-06CH11357.

The Argonne Wakefield Accelerator Facility is dedicated to the study of advanced accelerator concepts based on electron beam driven wakefield acceleration and RF power generation. The facility employs an L-band photocathode RF gun to generate high charge short electron bunches, which are used to drive wakefields in dielectric loaded structures as well as in metallic structures (iris loaded, photonic band gap, etc). Accelerating gradients as high as 100 MV/m have been reached in dielectric loaded structures, and RF pulses of up to 44 MW have been generated at 7.8 GHz. In order to reach higher accelerating gradients, and also be able to generate higher RF power levels, a photocathode with higher quantum efficiency is needed. Therefore, a new RF gun with a Cesium Telluride photocathode will replace the electron gun that has been used to generate the drive bunches. In addition to this, a new L-band klystron will be added to the facility, increasing the beam energy from 15 MeV to 23 MeV, and thus increasing the total power in the drive beam to a few GW. The goal of future experiments is to reach accelerating gradients of several hundred MV/m and to extract RF pulses with GW power level.

• S.P. Antipov, W. Gai, J.G. Power
  ANL, Argonne
• A. Kanareykin, P. Schoessow
  Euclid TechLabs, LLC, Solon, Ohio
• G. Semouchkin, E. Semouchkina
  PSU, University Park, Pennsylvania
• A.V. Tyukhtin
  Saint-Petersburg State University, Saint-Petersburg

Funding: DOE

Metamaterials (MTMs) are periodic artificially constructed electromagnetic structures. The periodicity of the MTM is much smaller than the wavelength of the radiation being transported. With this condition satisfied, MTMs can be assigned an effective permittivity and permeability. Areas of possible application of MTMs in accelerator science are Cherenkov detectors and wakefield devices. MTMs can be designed to be anisotropic and dispersive. The combination of engineered anisotropy and dispersion can produce a Cherenkov radiation spectrum with a different dependence on particle energy than conventional materials. This can be a basis for novel non-invasive beam energy measurements. We report on progress in the development of these media for a proof-of-principle demonstration of a metamaterial-based beam diagnostic.

• A.V. Tyukhtin
  Saint-Petersburg State University, Saint-Petersburg
• S.P. Antipov
  ANL, Argonne
• A. Kanareykin, P. Schoessow
  Euclid TechLabs, LLC, Solon, Ohio

Funding: SBIR DOE (DE-FG02-08ER85031); Russian Foundation for Basic Research (06-02-16442-a); Physical Faculty of St.Petersburg State University (Russia) (14.10.08)

We consider microwave Cherenkov radiation in a waveguide containing an engineered medium, and show that the properties of the radiation can be used to determine the energy of charged particle beams. These properties can form the basis of a new technique for bunch diagnostics in accelerators. We propose to use a material characterized by a diagonal permittivity tensor with components depending on frequency as in the case of a plasma but with the constant terms not equal to unity. These properties can be realized in a metamaterial with a relatively simple structure. In contrast to previous work in the present paper a vacuum channel in the waveguide is taken into account. The particle energy can be determined by measurement of mode frequencies. It is shown that a strong dependence of mode frequencies on particle energy for some predetermined narrow range can be obtained by appropriate choice of the metamaterial parameters and radius of the channel. It is also possible to obtain energy measurements over a wider range at the cost of a weaker frequency dependence.

*A.V.Tyukhtin, S.P.Antipov, A.Kanareykin, P.Schoessow, PAC07, p.4156.
**A.V.Tyukhtin, EPAC08, p.1302.
***A.V.Tyukhtin, Technical Physics Letters, v.34, p.884 (2008); v.35 (2009), in press.

• S.P. Antipov, W. Gai, O. Poluektov, J.G. Power
  ANL, Argonne
• A. Kanareykin, P. Schoessow
  Euclid TechLabs, LLC, Solon, Ohio
• L. Schächter
  Technion, Haifa

Funding: DOE

Particle Acceleration by Stimulated Emission of Radiation (PASER) is method of particle acceleration in which a beam gains energy from an active medium through stimulated emission. To obtain the required sitmulated emission for the PASER effect the particle beam intensity is modulated at the frequency corresponding to the energy difference between the levels in which population inversion is achieved in the active medium. We propose to use solid-state active medium based on the Zeeman effect (triplet systems) for the PASER. Modulation of the beam at the frequency of the transition to obtain stimulated emission can be produced by means of a deflecting cavity. A transverse "beamlet" pattern will be produced on the AWA photocathode gun by using a laser mask. The transverse beam distribution will be transformed into a longitudinal beam modulation as the beam passes through the deflecting cavity. In this paper we report on the development of active media and the first RF bench test.