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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

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

2. Coherent Synchrotron Radiation


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


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 [email protected]

user optics


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.


measured a / fs-tuning

synchrotron frequency

vers rf-detuning

synchrotron frequency

vers Dp/p

octupole excited

octupole excited

long. chrom corr.

long. chrom corr.


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 !


information

from THz signals

THz-frequency domain

Fourier spectrometer

THz-time domain

fast detectors


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


THz signals at 3 different a-settings

THz power is manipulated by a variation,

@ 30 mA beam current


30 mV & 20 ms

30 mV & 20 ms

9 mV & 20 ms

200 mV & 20 ms

appearance of CSR bursting in time domain


Csr signals in frequency domain 1
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


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


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


Mls scaling law

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:


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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