Exponential growth of self-amplified spontaneous emission at 530nm was first experimentally observed at the Advanced Photon Source low-energy undulator test line in December 1999. Since then, further detailed measurements and analysis of the results have been made. Here, we present the measurements and compare these with calculations based on measured electron beam properties and theoretical expectations.

N.D. Amol~ J. Attig, G. Banks, R. Bechtold, K. Becze~ C. Benson, S. Berg, W. Berg, S.G. Biedro~ J.A Biggs, M. Borlan@K. Boerste, M. Bose~ W.R. Brzowski,J. Buc& J.A. Carwardme, P. Castro#,Y.-C. Chae, S. Christensen, C. Clark M. Conde$,E.A.Crosbie, G,A. Decker, RJ. Dejus, H. DeLeon, P.K. Den Harto& B.N. Deriy, D. Dohan, P. Dombrowski,D. Donkers, C.L. Doose, RJ. Dortwe~ G.A. Edwards, Y. Eidelman, M.J. Erdmann, J. Error, R Ferry, R, Flood, J. Forrestal, H. Freund+,H. FriedSam,J. Gagliano, W. Gai$, J.N. Galay@ R. Gerig, R.L. Gihnore, E. Gluskm,G.A. Goeppner, J. Goetzen, C. Gold, A.J. Gorski, A.E. GrelicL M.W. Hahne, S. Hanusk%K.C. Harkay, G. Harris, A.L. Hillman,R Hogrefe, J. Hofi Z. Huang, J.M. Jagger, W.G. Jansmq M. Jaski, S.J. Jones, R.T. Keane, A.L. Kelly,C. Keyser, K.-J. Kim, S.H. Kim, M. Kirshenbaum, J.H. Klic~ K. Knoerzer, R.J. Koldenhoven, M. KnoK S. Labu~ R Laird, J. Lang, F. Lenkszus, E.S. Lessner, J.W. Lewellen,Y. Li, R.M. Lill, A.H. Lurnpkin,O.A. Makarov, G.M. Markovich, M. McDowell, W.P. McDowell, P.E. McNarnaq T. Meier, D. Meyer, W. Michalek, S.V. Milton*,H. Moe, E.R. Moog, L. Morrison, A. Nassiri, J.R. Noonan,R. Otto, J. Pace, S.J. Pasky, J.M. Penickz A.F. Pietryl% G. Pile, C. Pitts, J. Powe#, T. Powers,C.C. Putnam, A.J. Puttkammer, D. Reigle, L. Reigle, D. Ronzhin, E.R. Rotelz E.F. Russell, V. Sajaev, S. Sarkar, J.C. Scapino, K. Schroeder,R.A. Seglem, ?4.S.Serene, S.K. SharmA J,F. Sidarous, O. Singh,T.L. Smith, R. Soliday, G,A. SpraWS.J. Stein, B. Stejskal, V. Svirtun, L.C. Teng, E. Theres, K. Thompson, B.J. Tieman, J.A. Torres, E.M. Trakhtenberg, G. Travish, G.F. Trento, J. Vacc% LB. Vasserman, N.A. Vinokurov+,D.R. Walters, J. Wang, X.J. Wang:, J. Warren, S. Wesling, D.L. Weyer, G. Wiemerslage, K. WilheWI, R Wright, D. Wynco~ S. Xu, B.-X. Yang W. Yoder, RB. Zabel

The APS linac beam energy must be stable to within /spl plusmn/1% to match the energy acceptance of the positron accumulator ring. The klystron pulse modulators must therefore provide a pulse-to-pulse repeatability of 0.1% in order for the beam to have the required energy stability. The modulators have had difficulty achieving the necessary repeatability since the pulse forming network (PFN) charging scheme does not include a deQing circuit. Several of the major charging circuit components are also less reliable than desired. In order to increase operating reliability and to improve pulse-to-pulse stability, it is planned to replace the high voltage power supplies in all modulators with constant-current power supplies. A new modulator charging supply that contains two EMI series 303 constant-current power supplies was constructed.

A statistical methodology is presented for predicting drive performance based on fundamental static friction (stiction) measurements. The technique allows the prediction of drive stiction and dynamic friction failures, based on component level spinstand measurements. We discuss both the fundamental measurement of component stiction and the interpretation of the results as applied to an actual disk drive. The component measurements examine the effects of acceleration, filtering and sampling. It is shown that motor acceleration and the electronic configuration of the test stand affect the stiction measurement, but by proper electronic and mechanical designs this effect can be reduced to an insignificant quantity. The interpretation of component results considers incorporating the effect of multiple heads in a drive, and a statistical model is devised that accounts for both static and dynamic friction variation, along with motor/driver variations. One can predict the probability of a single drive failure or the failure rates of a population of drives, either new or after extensive field exposure. We show that a poorly, characterized measurement compared to an arithmetic average of the available motor torque may predict drive failure rates in error by several orders of magnitude.