Low Alpha & CSR in the MLS (PTB) G. Wüstefeld (BESSY) et al, ESLS XVI, Daresbury, Nov 28th. 2008 1...

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Low Alpha & CSR in the MLS (PTB)

G. Wüstefeld (BESSY) et al, ESLS XVI , Daresbury, Nov 28th. 2008

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

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content

1. Low alpha optics

2. Coherent Synchrotron Radiation

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The Metrology Light Source (MLS)

of the PTB (German National Metrology Institute)

3rd sextupole family octupole family

low alpha tuning 3rd sextupole & 1 octupole families

E= 100 MeV to 630 MeV2R = 48 m

4 cell DBA

field 2500T/mlength 0.1m

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MLS low alpha optics

vers Q1-current 630 MeV@500kV

tuning range of low alpha optics4.4 < fs< 145 kHz0.0001 < 0.12

low alpha optics user optics

quad1-current/A

user optics

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2 chrom. sextupole fam.

3 chrom. sextupole fam.

1 chrom. octupole fam.

low alpha tuning by sextupoles and octupoles

keep away from zero!

MAD simulation, MLS TDR, 2003

0.0

0.0

01

0

.00

2

0.0

03

-2.0 -1.0 0.0 1.0 2.0

p/p

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measured fs-tuning

long. chrom corr.

octupole excited

synchrotron frequency vers rf-detuning

synchrotron frequency vers p/p

long. chrom corr.

octupole excited

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IR beam line at MLS

THz beam spot

acceptance 64x43 mrad 2

THz detector

Si-bolometerrise time ~1 msfrequency 0.1 – 15 THzNEP ~10 W/Hz -13

InSb-detectorrise time ~1sfrequency 0.1 – 1.5 THzNEP ~10 W/Hz -12

THz beam line still under construction !

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information from THz signals

THz-frequency domain Fourier spectrometer

THz-time domainfast detectors

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THz signals at MLS: time domain

modulated THz signal

FTS

(bursting) THz signal THz detector

pow

er

time

frequency

FFT

THz signals at MLS: frequency domain

THz signal THz detector

osci

pow

er

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THz signals at 3 different settings

THz power is manipulated by variation,

@ 30 mA beam current

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30 mV & 20 ms 30 mV & 20 ms

9 mV & 20 ms 200 mV & 20 ms

appearance of CSR bursting in time domain

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CSR signals in frequency domain-1

50 kV

400 kV

bursting threshold

630MeV

voltage scan 50 kV to 400 kV, 0.16mA SB, 630 MeV

THz-signal frequency40 kHz0 kHz

400 kV

50 kV

rf-v

olta

ge

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60 kV

500 kV

60 kV

500 kV

500 kV

60 kV

70 kV

70 kV

110 kV

CSR bursting signals in frequency domain-2

630MeV

630MeV

630MeV 630MeV

bursting threshold

bursting threshold ??

bursting threshold ?? bursting threshold

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Bursting thresholds measured at MLS

variation of current, bunch length, voltage, energy

BESSY fit

coloured dots indi-cate different sets of measurement

I~ 3/8

I~ 3/7

rms

nat.

bunc

h le

ngth

x 1

.7 /

mm

scaled current~ I / V f1/3

rev

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MLS scaling law

= zero-current-bunch length V = rf-voltageI = current per bunch

= 1.0 mmV = 250 kV I = 0.33 mA

0

0

0

includes many parametersit can be expressed as:

=bunch length, =moment. comp. factor, c=speed of light, f = syn.frequency,e=unit charge, V’=voltage gradient, 2R=circumference, E=energy

s

= [(V I )/(V I 0 0 03/7

=c /(2f ) , f = (ec V )/(2RE)

e s s2 2 ′

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Conclusion:

the low alpha optics extends the usage of storage rings to intense THz and short X-ray pulses

the low alpha optics works excellent

the bursting scales as predicted

coherent THz radiation as a diagnostics tool delivers sensitiveand new information on beam dynamics

Low Alpha & CSR in the MLS (PTB) G. Wüstefeld (BESSY) et al, ESLS XVI, Daresbury, Nov 28th. 2008 1...

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