Evolution of FEL and Driver

Upgrade Scenarios - D. 75 MeV System Performance

As with the 42 MeV system, the performance can be broken out into four categories:

A. Linear Optics

B. Aberration Analysis

C. Chromatic Behavior

D. Geometric Behavior

E. Error Sensitivity

Each will be addressed in turn.

A. Linear Optics

Beam envelopes and dispersions are well confined throughout the acceleration and energy recovery cycle. Peak envelopes are under 25 m and peak dispersions of order 2 m, as shown in the following figure.

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B. Aberration Analysis

Second order transport matrix elements meet the same requirements imposed on the 42 MeV transport. All aberrations are of acceptable magnitude, and are shown in the following tabulation of the wiggler to linac matrix.

FIRST ORDER MATRIX

  -.1568291E+01  -.1796152E+01   .1903416E-15  -.2368843E-15   .0000000E+00  -.8330534E-14
   .4760121E+00  -.9246378E-01  -.1756378E-15   .2011789E-16   .0000000E+00  -.6383782E-15
  -.3998739E-15   .2501536E-17   .3537885E+01  -.6089684E+00   .0000000E+00   .3551035E-14
   .7542575E-16   .9399933E-16  -.2050681E+00   .3179527E+00   .0000000E+00  -.2331498E-15
   .1471046E-14   .2109424E-14  -.9665309E-16   .3522211E-15   .1000000E+01   .6130274E-02
   .0000000E+00   .0000000E+00   .0000000E+00   .0000000E+00   .0000000E+00   .1000000E+01

SECOND ORDER TERMS

   .1921703E+02  -.1429603E+02   .2350750E-13   .3071450E-02   .0000000E+00  -.2954316E+02
                 -.3753006E+01   .4078858E-14  -.5115337E-04   .0000000E+00   .7816742E+01
                                -.9440359E+02  -.3388496E+02   .0000000E+00  -.1702872E-12
                                                .5097362E+01   .0000000E+00  -.2484371E-13
                                                               .0000000E+00   .0000000E+00
                                                                             -.2633394E-13
  -.1739085E+01  -.1910358E+01   .9946539E-14  -.1355655E-04   .0000000E+00  -.1564568E+01
                  .4665986E+00  -.1093305E-14  -.1810875E-03   .0000000E+00  -.2422633E+01
                                -.1470521E+02   .6537205E+01   .0000000E+00  -.1661958E-13
                                               -.3888192E+00   .0000000E+00   .1092301E-13
                                                               .0000000E+00   .0000000E+00
                                                                              .2182976E-13
   .2548669E-02  -.1090898E-02  -.1036116E+03   .9277441E+01   .0000000E+00  -.5845909E-13
                 -.5670005E-03   .3109460E+02   .7819068E+00   .0000000E+00   .3478907E-13
                                -.2107001E-13  -.6186512E-14   .0000000E+00  -.7070766E+02
                                               -.7470295E-14   .0000000E+00  -.9634389E+02
                                                               .0000000E+00   .0000000E+00
                                                                             -.3522655E-13
  -.1477297E-03   .6323225E-04   .4445115E+02   .1122630E+01   .0000000E+00   .3190693E-13
                  .3286532E-04   .8192472E+01  -.4249972E+01   .0000000E+00   .3619951E-14
                                 .8143882E-14   .8233187E-14   .0000000E+00   .4266258E+02
                                               -.1622275E-16   .0000000E+00   .4595567E+01
                                                               .0000000E+00   .0000000E+00
                                                                              .3338318E-13
   .7885038E+01  -.7764608E+00  -.3792261E-13  -.6185261E-14   .0000000E+00  -.9088838E-13
                  .2620130E+01  -.1517351E-13   .2026905E-14   .0000000E+00  -.7052554E-13
                                 .6784444E+02  -.3374053E+01   .0000000E+00   .8594168E-13
                                                .1381995E+02   .0000000E+00  -.1212962E-13
                                                               .0000000E+00   .0000000E+00
                                                                             -.4658139E-15

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C. Chromatic Behavior

As in the 42 MeV system, the chromatic variations of beam and lattice parameters are acceptable. Results for a momentum scan in the wiggler to reinjection transport are presented below.

Momentum scan of beam and orbit parameters through wiggler to reinjection transport

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D. Geometric Behavior

The upgraded system shows little phase space distortion, even at 10 times the design (13 mm-mrad, normalized) emittance. Results for wiggler to reinjection point tracking of the phase space at 10 times design emittance at each of seven momenta in 1% steps between -3% and +3% are shown below.

Geometric aberration analysis: phase space from wiggler to cryomodule in 1% momentum steps from -3% to +3%.

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E. Error Sensitivity

The general error budget for the upgraded machine is similar to that for the 42 MeV system. Error effects may be enhanced ~20-50% or so due to the greater length and larger parts count of the 75 MeV system.

The use of two modules introduces the need for a tracking tolerance on the RF gradients/module energy gains. Asymmetry in module gradient might need to be limited. The system will need the same energy at the triplet between the module during energy recovery (to within a few percent, as opposed to a few tens of percent) as during acceleration, so that the quads do not over- or under-focus, cause mismatch, and lead to excessive spot size growth. Preliminary simulations of this effect indicate that there is some sensitivity to this constraint; module energy gains of 35 and 30 MeV may be acceptable, while gains of 40 and 25 MeV are probably not acceptable.

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In the FODOmat's A Guide to the Design,

	Project Overview
	System Design Process
	Application of Process to High Power IR FEL
	Description of Solution
	System Performance
	Error Studies
	Upgrade Scenarios
	A. System Evolution
	B. 75 MeV Upgrade Analysis
	C. Design Solution for 75 MeV
**you are here! **	D. 75 MeV System Performance
**the next link is	E. Upgrades to UV and High Power IR

	Go to The FODOmat's FEL Page

Last modified: 10 March 1997
http://www.jlab.org/~douglas/ is maintained by: douglas@jlab.org