1. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 1 A. Hoehl, R. Klein, R. Müller, G. Ulm PTB Berlin (Germany) Low-  Operation of the Metrology Light Source* J. Feikes, M. Ries, P.O. Schmid, G. Wüstefeld HZB Berlin (Germany) ICFA Workshop on Future Light Sources, March 5-9, 2012 Thomas Jefferson National Accelerator Facility, Newport News, VA (USA) * J. Feikes et al., PRSTAB-14, 030705 (2011)

2. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 2 Outline - MLS overview - MLS low-  optics -  -buckets -THz measurements - Summary MLS building of the MLS is owned by : and operated by :

3. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 3 MLS machine energy / MeV< 630 circumference / m48 rf frequency / MHz500 max. rf Voltage / kV500 current 1e …200mA life time / hours ~10 max. bunches 80 nat. emitt. / nmrad 100 main MLS parameter scheme of the ring octupole MLS: the first machine optimized for coherent THz-radiation

4. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 4 MLS beam optics user optics,  =0.03low alpha optics,  =0 optical functions 4-pole 6-pole 8-pole 2-pole  expansion  =  (  )  =  0 +  1  +  2  2 … magnet types: Disp.=0 crossing of chromatic orbits  =  p/p 0 rel. momentum deviation control of 3 leading  -terms: quadrupoles sextupoles (3 fam.) octupoles (1 fam.) ->  0 ->  1 ->  2 definition of  : L=L 0 (1+  p/p 0 )  =momentum compaction factor

5. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 5  -series  expansion control of higher order terms of  =  0 +  1  +  2  2 rel. momentum deviation / % 2 4 6 8 10 12 14 16 18 20 mom. comp. factor / 10 -4 -2 -1 0 1 2  =  (  p/p 0 ) MAD-8 simulation 1 2 3 -4 -2 0 2 4 rf-frequency change  f rf / kHz synch.-frequency f s / kHz 2 4 6 8 10 12 14 16 18 20 f s = 9.5 kHz  0 = 4.6x10 -4 f s = f s (  f rf )MLS measurements 2 3 -> : curvature of  =  (  ) ->  2, adjusted by octupoles 23 -> : slope of  =  (  ) ->  1 =0, adjusted by sextupoles 21 octupole off octupole on

6. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 6 effect of octupole setting on lifetime life time as a function of octupole current Low-  operation and octupole control figure parameters: E=250 MeV, V rf =125kV, I MB =20mA calibration: octupole current=-8A ->  2 =35 for comparison: MLS user optics  0  = 330x10 -4 - octupoles required !! - life time improves substantially for  0  < 2.5x10 -4     o bucket ‘A’bucket ‘C’

7. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 7  -buckets - simplified Hamiltonian - FP=fixed points (  ) at  1 =0: phase space at transition  0  > 0   0  < 0 H 0 =eV rf f rev /E 0 - double beam:  -buckets: (, ) D. Robin et al., Phys. Rev. E 48, 2149 (1993) rf-buckets: (, )

8. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 8  -buckets small amplitude bunch parameters, derived from Hamiltonian: bucketFP ( ,  )fsfs  A(0,0) f s0 00 > 0 B (  1 =0) (0, ) f s0  0 < 0 C( ,0)f s0 00 < 0 B 2 C B 1 picture of triple beam at beam profile monitor f s0 2 = f rev H 0  0 /2   0  2  rf f s0  /H 0

9. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 9  -buckets C B1B1 B2B2 C B triple beam  1 = 0 synchrotron side bands of triple beam ratio of synchrotron tunes = B 2 C B 1 14.6 kHz 20.7 kHz -> talk M. Ries et al., TUOAB02, IPAC 2011 triple beam  1 = 0

10. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 10  -buckets topping up with  -buckets the electron flow rate from bucket B 2 to bucket B 1 is controlled by feedback of the rf-frequency, to keep the bucket B 1 current constant within 2 % over 10 h. -> M. Ries et al., ICFA Beam Dynamics Mini Workshop on Low Emittance Rings, 2011 B1B1 B2B2 ACC electron flow from B 2 to B 1 by master clock manipulation  /  rad  / % B 1 -current (red line) as a function of time, the sum current B 1 +B 2 is indicated by the black line. B 1 -current B 1 +B 2 -current I B1 / mA time / h I sum / mA

11. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 11 - no beam loss at  0  =0 crossing! - strong correlation between Q 1 -current & THz power, THz power shows strong maximum - small dip in beam life time at max. THz power, followed by large dip in lifetime - cross section increase indicates double beam, (spurious dispersion in the vertical plane) quad Q 1 current scan, crossing  0 = 0 (Q 1 acts on dispersion) Transition  0  > 0   0  < 0  I/I = 0.5%

12. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 12 bursting THz power I**2, -> bunch size changes with current CSR power vs. beam current (bursting CSR) at 120 mA an average power of max. 60 mW achieved, measured with a calibrated power meter. THz CSR measurements 20 60 100 140 1 2 3 4 5 beam current / mA THz power /arb. units linear fit: P THz ~0.86+0.031*I linear increase of THz power with bunch current.

13. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 13 CSR power spectrum Spectral range 1.4 1/cm (not shown in fig.) to 50 1/cm. incoherent signal mixed with coherent signals, corrected gain = 100,000 THz CSR measurements corrected gain = 100,000 THz beam port at the MLS beam line THz detector FTIR spectrometer IR microscope Example of hardware setup at the THz beam port. Different types of detectors are available. Experiments: detector characterization and development (partly in cooperation with DLR (Berlin) and KIT (Karlsruhe)) and spectroscopy.

14. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 14 CSR bursting measurement CSR in time domain (example) CSR bursting threshold detected while increasing rf-Voltage amplitude, (0.5 mA SB-current) bunch length as a function of scaled sb-current: -> MLS data is offset with respect to coasting beam theory bursting thresholds MLS and BESSY II zero current bunch length / ps BESSY II data points theory all other points MLS data ~ scaled sb-bunch current I

15. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 15 Summary - the MLS is the first storage ring optimized for CSR - successful control of 3 orders of  - no beam loss at the  0 = 0 crossing - beam can be stored in 3 types of  -buckets - stable and bursting THz-CSR can be produced - bursting thresholds agree fairly well with theory

16. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 16

17. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 17 1 kHz corresponds to a σ of 1.9 ps. P. Kuske et al., PAC 2003

18. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 18 IR/THz Strahlrohre an der MLS IR THz IR THz Undulator-IR X-ray and IR Spectrometry

19. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 19 THz CSR measurements THz-power Lifetime / h  -h / mm  -v / mm  f rf / Hz bunch current / mA beam parameters during low alpha current decay mode

20. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 20 THz-signal & beam parameters versus rf-voltage scan @ 250 MeV & 10 kHz rf-voltage FWHM-x FWHM-y current THz-signal Pos-x Pos-y time / seconds arb. unit rf-scan: 75 kv - 430 kV current: 0.8 mA THz – signal: THz beam line ~2 mm iris aperture mech. chopper 80 Hz 250MeV, 250kV, 10kHz    =0.44ps ! suppressed THz signal THz CSR measurements

21. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 21 reproducibility of the THz / low-  optics 13 beam injections cycles beam current THz power / arb. units 150 100 50 beam current / mA 0 -50 -30 -10 time / hours THz CSR measurements After injection, the decay pattern of the THz signals repeats.

22. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 22 definition of  : L=L 0 (1+  p/p 0 ) longitudinal beam dynamics & low-  optics non-isochronous ring momentum dependent revolution time  =0 for short bunches L = orbit length p = electron momentum  = momentum compaction factor starting point, short bunch long bunch, ½ revolution 2  p/p isochronous ring  =0 momentum independent revolution time starting point, short bunch short bunch, ½ revolution Momentum compaction factor  crossing of chromatic orbits

23. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 23 BESSY II bursting thresholds CSR bursting measurements BESSY II comparison with theory scaled single bunch current  A / MV Nov. 2011 Jan. 2012 before 2003 BCS:  =0.5+0.34  +dip 10 8 6 4 2 1 1 10 100 1000 zero current rms bunch length / ps coasting beam theory

24. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 24 stable and bursting CSR bursting stable choppedunchopped InSb time domain signals recorded on an oscilloscope, stable and bursting CSR is detected. CSR power time THz CSR measurements

25. G. Wüstefeld (HZB, Berlin) et al., MLS Low- , Future Light Sources, March 5-9, 2012, Jefferson Lab, USA 25 “Isochronous apparatus”, Jean Truchet, 1699 Museum of the History of Physics, Padua (Italy) Museum of the History of Science, Florence (Italy) History Figure by courtesy of the Museum of the History of Physics, Padua (Italy) marble run: the revolution frequency is independent of the orbit