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On the evaluation of modified Bessel functions of the second kind and fractional order for synchrotron radiation calculations

On the evaluation of modified Bessel functions of the second kind and fractional order for synchrotron radiation calculations
On the evaluation of modified Bessel functions of the second kind and fractional order for synchrotron radiation calculations
The modified Bessel functions of the second kind and fractional order K1/3(x) and K2/3(x) are of importance in the calculation of the frequency spectrum of synchrotron radiation. The parameter range of interest is typically 10-6<x<10. Recently, there has been particular interest in the generation of ‘terahertz’ radiation, which can be coherently enhanced by many orders of magnitude when the electron bunch length is shorter than the terahertz wavelength. This requires evaluation of the Bessel functions for small values of the argument. It is shown that the series commonly used to evaluate these functions has poor convergence properties under these conditions. An alternative series is derived which has much better convergence for x<1.
bessel functions, synchrotron radiation, terahertz, infrared
0168-9002
431-436
Rutt, H.N.
e09fa327-0c01-467a-9898-4e7f0cd715fc
Rutt, H.N.
e09fa327-0c01-467a-9898-4e7f0cd715fc

Rutt, H.N. (2003) On the evaluation of modified Bessel functions of the second kind and fractional order for synchrotron radiation calculations. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 511 (3), 431-436. (doi:10.1016/S0168-9002(03)01929-6).

Record type: Article

Abstract

The modified Bessel functions of the second kind and fractional order K1/3(x) and K2/3(x) are of importance in the calculation of the frequency spectrum of synchrotron radiation. The parameter range of interest is typically 10-6<x<10. Recently, there has been particular interest in the generation of ‘terahertz’ radiation, which can be coherently enhanced by many orders of magnitude when the electron bunch length is shorter than the terahertz wavelength. This requires evaluation of the Bessel functions for small values of the argument. It is shown that the series commonly used to evaluate these functions has poor convergence properties under these conditions. An alternative series is derived which has much better convergence for x<1.

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Published date: 2003
Keywords: bessel functions, synchrotron radiation, terahertz, infrared
Organisations: Optoelectronics Research Centre

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Local EPrints ID: 13836
URI: http://eprints.soton.ac.uk/id/eprint/13836
ISSN: 0168-9002
PURE UUID: e44fdc40-d9fb-45fa-80f7-0a8ae0bb0386

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Date deposited: 13 Jan 2005
Last modified: 15 Mar 2024 05:13

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Author: H.N. Rutt

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