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Low Alpha Optics and Coherent Synchrotron Radiation in the MLS

Low Alpha Optics and Coherent Synchrotron Radiation in the MLS J. Feikes, M. v. Hartrott, G. Wüstefeld (BESSY) A. Hoehl, R. Klein, R. Müller, G. Ulm (PTB) BESSY & PTB, Berlin (Germany)  PTB = German National Metrology Institute. content. 1. Low alpha optics.

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Low Alpha Optics and Coherent Synchrotron Radiation in the MLS

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  1. Low Alpha Optics and Coherent Synchrotron Radiation in the MLS J. Feikes, M. v. Hartrott, G. Wüstefeld (BESSY) A. Hoehl, R. Klein, R. Müller, G. Ulm (PTB) BESSY & PTB, Berlin (Germany)  PTB = German National Metrology Institute

  2. content 1. Low alpha optics 2. Coherent Synchrotron Radiation

  3. The Metrology Light Source (MLS) of the PTB (German National Metrology Institute) low alpha tuning  3rd sextupole & 1 octupole families field 2500T/m length 0.1m E= 100 MeV to 630 MeV 2pR = 48 m 4 cell DBA octupole family 3rd sextupole family

  4. a  quad1-current/A MLS low alpha optics low alpha optics user optics tuning range of low alpha optics 4.4 < fs< 145 kHz 0.0001 < a < 0.12 a vers Q1-current 630 MeV@500kV user optics

  5. a 0.0 0.001 0.002 0.003 -2.0 -1.0 0.0 1.0 2.0 Dp/p low alpha tuning by sextupoles and octupoles MAD simulation, MLS TDR, 2003  keep a away from zero! 1 chrom. octupole fam. 3 chrom. sextupole fam. 2 chrom. sextupole fam.

  6. measured a / fs-tuning synchrotron frequency vers rf-detuning synchrotron frequency vers Dp/p octupole excited octupole excited long. chrom corr. long. chrom corr.

  7. Si-bolometer rise time ~1 ms frequency 0.1 – 15 THz NEP ~10 W/Hz InSb-detector rise time ~1 ms frequency 0.1 – 1.5 THz NEP ~10 W/Hz -13 -12 IR beam line at MLS 2 acceptance 64x43 mrad THz detector THz beam spot  THz beam line still under construction !

  8. information from THz signals THz-frequency domain Fourier spectrometer THz-time domain fast detectors

  9. THz signals at MLS: time domain power osci (bursting) THz signal THz detector time THz signals at MLS: frequency domain FTS FFT power THz signal modulated THz signal frequency THz detector

  10. THz signals at 3 different a-settings THz power is manipulated by a variation, @ 30 mA beam current

  11. 30 mV & 20 ms 30 mV & 20 ms 9 mV & 20 ms 200 mV & 20 ms appearance of CSR bursting in time domain

  12. CSR signals in frequency domain-1 630MeV 400 kV bursting threshold 50 kV voltage scan 50 kV to 400 kV, 0.16mA SB, 630 MeV 400 kV rf-voltage 50 kV 40 kHz 0 kHz THz-signal frequency

  13. CSR bursting signals in frequency domain-2 630MeV 630MeV 60 kV 60 kV bursting threshold ?? bursting threshold 500 kV 500 kV 630MeV 630MeV 500 kV 70 kV 110 kV 60 kV 70 kV bursting threshold ?? bursting threshold

  14. 3/8 3/7 ~ ~ I I rms nat. bunch length x 1.7 / mm scaled current ~ I r / V f 1/3 rev Bursting thresholds measured at MLS variation of current, bunch length, voltage, energy BESSY fit coloured dots indi- cate different sets of measurement

  15. 3/7 s / s = [(V I )/(V I )] 0 0 0 s = 1.0 mm V = 250 kV I = 0.33 mA 0 0 0 s=bunch length, a=moment. comp. factor, c=speed of light, f = syn.frequency, e=unit charge, V’=voltage gradient, 2pR=circumference, E=energy s =acs /(2pf ) , f = (eac V )/(2pRE) s 2 2 ′ s s e MLS scaling law s = zero-current-bunch length V = rf-voltage I = current per bunch s includes many parameters, it can be expressed as:

  16. Conclusion: the low alpha optics works excellent the bursting scales as predicted coherent THz radiation as a diagnostics tool delivers sensitive and new information on beam dynamics the low alpha optics extends the usage of storage rings to intense THz and short X-ray pulses

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