The Metrology Light Source - Status Jörg Feikes, Paul Goslawski, Tobias Goetsch, Markus Ries, Martin Ruprecht, Gode Wüstefeld, Helmholtz-Zentrum Berlin, Germany J. Feikes et al., Phys. Rev. ST Accel. Beams 14, 030705 - Published 22 March 2011 R. Klein et al., Phys. Rev. ST Accel. Beams 11, 110701 - Published 20 November 2008
Bird eyes View of HZB Adlershof BESSY II Metrology Light Source (MLS)
MLS machine U125 (new) undulator kicker E / MeV = 50 (new) - 630 C / m = 48 I e / ma = 200 ε design / nmrad = 100 @600 MeV injection septum rf cavity, HOM damped 500 kv, 500 MHz 100 MeV microtron
Flexible and Standard Operation Schedule 2014 2014: distribution Standard and Flexible operation weeks flexible -weeks: operation modes adapted to needs of (often) single user But: strong demand on beam time by all users (= owners of MLS!) 4
Beam Time Schedule: Standard User Week Also in standard weeks there are special -mode shifts nights are used in unattended shifts no user operation on weekends machine commissioning standard user operation special
Definition of a Standard User Optics and Setup Together with beamline scientists standard setup for user operation was defined: standard user optics Parameter under investigation and related criteria for user operation: source size -> σ_z=250 µm -> flux and resolution source stability -> signal to noise ratio at source point lifetime!! -> reproducibility and temporal stability
Improving Lifetime of the Standard User Optics As a result of a diploma thesis (Tobias Goetsch) the lifetime in standard user optics could be considerably increased (-> talk by Tobias) = real improvement for many users! 7
Beamlines and experimental stations at the MLS Wavelength range at MLS Extreme UV to far-ir (4 nm to 7 mm) at 6 user beamlines -> different Op-modes varying user conditions @ flexible operation beam current :1e (1pA) 200 ma beam energy : 105 MeV 630 MeV momentum compaction factor: 0.033-0.00005 different emittances/beam sizes: 40 500 nmrad / σ_z = 100µm 2000µm, σ_s= 1 40 ps 1a 1 b 1c 1 d 1e 2a (undulator) IR radiation / laser for Comptonbackscattering deflected undulator radiation (IR/VIS) deflected undulator radiation (high-flux experiments) direct undulator radiation / Compton backscattering UV/VUV monochromator for undulator radiation direct calculable bending magnet radiation 2 b 3 4 5 6 7 UV/VUV monochromator (source calibration) EUV plane-grating monochromator UV/VUV monochromator (detector calibration) THz beamline IR beamline diagnostics frontend 8
The Operation Master a State Machine Operation Master performs transition analyzes actual machine state checks that all subystems are ready transition to ramp state ramps down to injection energy switch on systems for injection injects to desired current and ramps up to desired energy switches off sub-systems not needed performs transition to desired machine state configures and starts sub-systems for user run 9
Example of Operation modes MLS: rapidly increasing demand on beam time in low alpha optics -> Bunchlength/ps in standard user and low alpha optics (streak camera measurements) Thz power in low alpha mode Gain >10E5 Can low alpha mode made be compatible to standard user needs? 10
User Compatibility of Low Alpha Mode beam current @low alpha =190mA at excellent lifetime due to larger source size -> OK Insertion U125 can be closed to lowest gap in low alpha@630 MeV (ΔQy=0.06!) (after improving tunefeedforward) but effect on THz performance is still unclear -> under investigation Performance of low alpha mode on EUV beamline (= most demanding BL) o o o lower intensity due to higher emittance in low alpha intensity current dependent due to current dependent beam widening with increasing energy spread (if Dx 0 at source point) signal/noise ratio worse because longitudinal bursting translates into transverse oscillations of the source point o but: intensity can be recovered by - lower emittance - smaller energy width - smaller transversal divergence 11
User tailered Optics Idea: develop user tailed optics so that each user mode (as low alpha) can be adapted to the needs of as many users as possible - by shaping optical functions locally (all Quadrupoles are individually powered) - by adjusting the beam emittance - by adjusting the energy spread and bunch length -. optional position for Robinson Wiggler M. Ries: could be achieved using a Robinson Wiggler -> talk by Tobias Goetsch 12
Measuring Energy Spread energy spread has important impact on user performance can be measured fast and easy by determing horizontal beam size at position with non-zero dispersion using imaging system dispersive contribution to horiz. source size (calibration performed) 13
Scan of Beam Parameter vs. Energy Spread application: scan energy spread vs cav-voltage vs beam current 14
Operational Issues beamtime loss/min in 2013 vs components -> problem w gun cathode at microtron -> new test stand allows testing of cathode modifications and allows pre-conditioning 2013 DIA; 225; 4% BPR; 149; 2% KLWA; 158; 2% PHY; 189; 3% IT; 217; 3% Zeit der Vorfälle pro Komponentengruppe in min EXP; 135; 2% MPS; 73; 1% HF; 342; 5% MLT; 601; 9% VAC; 198; 3% FACI; 235; 4% microtron MPS HF MLT VAC FACI MIC IT PHY KLWA BPR DIA EXP MIC; 4117; 62% 15
Operational Issues II since an access to the acc-tunnel in August energy ramping accompanied by beam losses ramping capability only recovered after intense work on the procedure - many modifications necessary - slower ramp (6 min instead of 2 min), MB-Feedback now has to be used during ramp,. real cause for this problem is still unknown -> lot of (to some extent) contradicting observations (e.g. single bunch ramping not affected) 16
Thank you for your attention!