• R. Bonifacio, R. Bonifacio
  Universidade Federal de Alagoas, Maceio
• M. Ferrario
  INFN/LNF, Frascati (Roma)
• N. Piovella
  Universita' degli Studi di Milano, MILANO
• G.R.M. Robb
  Strathclyde University, Glasgow
• A. Schiavi
  Rome University La Sapienza, Roma
• L. Serafini
  INFN-Milano, Milano

Funding: Istituto Nazionale di Fisica Nucleare (INFN), Italy

Quantum effects in high-gain FELs become relevant when ρ'=ρ(mcγ/ ћ k)<1. The quantum FEL parameter ρ' rules the maximum number of photons emitted per electrons. It has been shown that when ρ'<1 a "quantum purification" of the SASE regime occurs: in fact, the spectrum of the emitted radiation (randomly spiky in the usual classical SASE regime) shrinks to a very narrow single line, leading to a high degree of temporal coherence. From the definition of ρ it appears that in order to achieve the quantum regime, small values of ρ, beam energy and radiation wavelength are necessary. These requirements can be met only using a laser wiggler. In this work we state the scaling laws necessary to operate a SASE FEL in the Angstrom region. All physical quantities are expressed in terms of the normalized emittance and of two parameters: the ratio between laser and electron beam spot sizes and the ratio between Rayleigh range and electron β-function. The feasibility study of a Quantum SASE FEL experiment using parameters as those foreseen in the SPARC/PLASMONX projects in construction at the INFN Frascati is explicitly discussed.

• H. Freund
  SAIC, McLean
• M. Abo-Bakr, K. Goldammer, D. Kraemer, B.C. Kuske, A. Meseck
  BESSY GmbH, Berlin
• S. Biedron
  ANL, Argonne, Illinois

The BESSY FEL is based on a seeded cascade of High Gain Harmonic Generation (HGHG) sections followed by an amplifier to produce coherent and stable short wavelength output. Here, we report on comparative design studies carried out using the MEDUSA [1], and GENESIS [2] simulation codes. These two codes have each been used to successfully predict a variety of FEL designs and have agreed well with a number of important experiments. In addition, they were included in a comparative study of FEL simulation [3] that reported substantial agreement between the codes for the specific configurations studied. However, these codes are based on different assumptions. GENESIS treats the particle dynamics using a wiggler-averaged orbit approximation, the transverse electromagnetic field is treated using a field solver, and harmonics are not included. MEDUSA does not use the wiggler-averaged orbit approximation to treat particle dynamics, the transverse fields are treated using a Gaussian modal superposition, and harmonics are included self-consistently. Hence, the comparative study for an HGHG cascade is important. We report the results where the parameters of each stage have been optimized.

[1] H.P. Freund et al., IEEE JQE 36, 275 (2000). [2] S. Reiche, NIMA 429, 243 (1999). [3] S.G. Biedron et al., NIMA 445, 110 (2000).

• Y. Tsunawaki
  OSU, Daito, Osaka
• M. Asakawa, N. Ohigashi
  Kansai University, Osaka
• K. Imasaki
  ILT, Suita, Osaka

We have been constructed a solenoid-induced helical wiggler for a compact free electron maser operated in a usual small laboratory which does not have electric source capacity available enough. It consists of two staggered-iron arrays inserted perpendicularly to each other in a solenoid electromagnet. In order to lead/extract an electron beam into/from the wiggler, adiabatic transition (AT) field is necessary at both ends of the wiggler. In this work the AT field was produced by setting staggered-nickel plates with different thickness in the five periods. The thickness of each nickel plate was decided by the field analysis using the MAGTZ computational code based on a magnetic moment method. Exact thickness was, however, found by the precise measurement of the field distribution with the greatest circumspection to obtain a homogeneous increment of the AT field. The change of AT field distribution was studied by referring to an equivalent electric circuit of the wiggler.

• S. Kashiwagi, G. Isoyama, R. Kato, N. Noda
  ISIR, Osaka
• K. Tsuchiya, S. Yamamoto
  KEK, Ibaraki

We apply the edge-focusing scheme to the wiggler for FEL and SASE in the far-infrared region at ISIR, Osaka University in order to make the gain length of SASE shorter by keeping the beam size small along the wiggler. As the electron beam energy is 10^-30 MeV and the magnetic field of the wiggler is up to 0.4 T, the natural focusing force in the vertical direction is strong in the wiggler and it is strongly dependent on the electron energy and the wiggler gap. The focusing forces should be compatible to or higher than the strong natural focusing force, equally in the horizontal and vertical directions over the wide range of the electron beam energy and the wiggler gap. In order to meet this requirement, we adopt the strong focusing scheme using the EF wiggler. The wiggler consists of 4 FODO cells in the 1.938 m long (32 periods, period length: 60mm). A focusing element and defocusing element are incorporate with single wiggler periods with edge angles of +5 and -5 degrees, respectively, and they are separated by 3 normal wiggler periods. The strong focusing wiggler has been fabricated and magnetic field has been measured at KEK. We will report results of the magnetic field measurements of the strong focusing wiggler.

• H. Freund
  SAIC, McLean

Funding: Work supported by ONR, NAVSEA, and the JTO

Time-dependent FEL simulations use a variety of techniques. Most simulations use a slowly varying envelope approximation (SVEA). One such technique assumes that the envelope varies only in z combined with a field representation as an ensemble of discrete harmonics, which is equivalent to a time-dependent simulation [1] but is computationally prohibitive. A second technique uses an SVEA in both in z and t [2]. The particles and fields are advanced in z using the same process as in steady-state simulations and then the time derivative describing slippage is applied. This is used in wiggler-averaged codes such as GINGER [3] and GENESIS [4]. We describe the inclusion of this technique in the non-wiggler-averaged code MEDUSA [5], which is applied to amplifiers and oscillators. MEDUSA differs from GINGER and GENESIS also in the way the field is treated. GINGER and GENESIS use a field solver and must explicitly propagate the field outside the wiggler oscillators. This is computationally intensive. MEDUSA uses a Gaussian mode ensemble; hence, there is no need to propagate the fields outside the wiggler, and MEDUSA is able to simulate FEL oscillators in 3-D using relatively modest computational resources.

[1] N. Piovella, Phys. Plasmas 6, 3358 (1999). [2] R. Bonifacio et al., Phys. Rev. A 40, 4467 (1989). [3] W. Fawley, LBID-2141, CBP Tech Note-104, UC-414, 1995. [4] S. Reiche, NIMA 429, 243 (1999). [5] H.P. Freund et al., IEEE JQE 36, 275 (2000).

• D. Li
  ILT, Suita, Osaka

The conventional cavity for a free-electron laser (FEL) oscillator forms Gaussian optical beam, transversely spreading along the interaction region. The transverse divergence will induce reduction of the FEL gain by three aspects: degenerating filling factor, causing diffraction loss and limiting the effective interaction distance. Bessel optical beam has been experimentally demonstrated diffraction-free characteristic, providing a possibility of improvement of FEL gain. In this paper, we present a conceptual design of a Bessel beam cavity for the free-electron laser. This cavity generates nondiffracting optical beam in the wiggler, which can improve the filling factor, decrease the diffraction loss and elongate the effective interaction distance.

• A.I. Al-Shamma'a, J. Lucas, A. Shaw, R.A. Stuart, C.C. Wright, M. Houghton
  University of Liverpool, Liverpool
• P. van der Slot
  University of Twente
• J. Hamelin
  University of Rennes

The objectives of this European project are to use high frequency microwave technology to develop focused energy sources for industrial applications. The microwaves, generated in the 10GHz to 20GHz frequency range by using a table top FEM has been used to investigate novel solutions for material processing and material production, including microwave heating of substrates, microwave chemistry for increasing the speed of thermal reactions, microwave plasma chemistry for aiding gaseous reactions in the reduction of combustion pollutants and the production of UV/ozone for germicidal activities. In this paper we report unique results and analysis in using tuneable FEM system compared with the conventional magnetron 2.45 GHz system.

• Y.K. Wu, J. Li, S. Mikhailov, V. Popov
  DU/FEL, Durham, North Carolina
• N. Gavrilov, G. Kulipanov, O.A. Shevchenko, N. Vinokurov, P. Vobly
  BINP SB RAS, Novosibirsk

Funding: This work is supported by the U.S. AFOSR MFEL grant F49620-001-0370 and by U.S. DOE grant DE-FG05-91ER40665.

To improve the capability and performance of its light sources, the Duke FEL lab (DFELL) is upgrading its storage ring based FEL by replacing the existing linearly polarized OK-4 FEL with the next generation OK-5 FEL which is capable of delivering both linearly and circularly polarized light. To reduce and manage the risk associated with this project, the FEL upgrade is carried out in three phases. In the second phase of upgrade in 2005, two OK-5 wigglers are installed in a specially designed lattice where OK-4 wigglers remain, forming a distributed optical klystron FEL with hybrid wiggler magnets. In this paper, we report our commissioning experience of this distributed optical klystron FEL, including its first lasing in visible wavelengths and measured lasing spectra and power. We will also present our first experimental results on the FEL polarization manipulation using OK-4 and OK-5 wigglers. In addition, we report the performance enhancement of the Compton gamma-ray source driven by this FEL and initial FEL operation experience for user applications.

• M. Goldstein, S.H. Lee, Y.A. Shroff, P.J. Silverman, D. Williams
  Intel, Santa Clara, California
• R. Pantell
  Stanford University, Stanford, Califormia
• H. Park, M.A. Piestrup
  Adelphi Technology, Inc., San Carlos, California

Funding: Intel Research

Semiconductor industry growth has largely been made possible by regular improvements in lithography. State of the art lithographic tools cost upwards of twenty five million dollars and use 0.93 numerical aperture projection optics with 193nm wavelengths to pattern features for 45 nm node development. Scaling beyond the 32 nm feature size node is expected to require extreme ultraviolet (EUV) wavelength light. EUV source requirements and equipment industry plasma source development efforts are reviewed. Exploratory research on a novel hybrid klystron and high gain harmonic generation FEL with oblique laser seeding will be disclosed. The opportunity and challenges for FELs to serve as a second generation (year 2011-2013) source technology in the semiconductor industry are presented.