Status of the ANKA Short Bunch Operation Anke-Susanne Mller - - PowerPoint PPT Presentation

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Status of the ANKA Short Bunch Operation Anke-Susanne Mller - - PowerPoint PPT Presentation

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Forschungszentrum Karlsruhe in der Helmholtz-Gemeinschaft Status of the ANKA Short Bunch Operation Anke-Susanne Mller Institut fr Synchrotronstrahlung (ISS), Forschungszentrum Karlsruhe Laboratorium fr Applikationen der

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SLIDE 1

Forschungszentrum Karlsruhe

in der Helmholtz-Gemeinschaft

Status of the ANKA Short Bunch Operation

Anke-Susanne Müller Institut für Synchrotronstrahlung (ISS), Forschungszentrum Karlsruhe

Laboratorium für Applikationen der Synchrotronstrahlung (LAS), Uni Karlsruhe

UVSOR, 24/9/2007 Short Bunches at ANKA page 1

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SLIDE 2

Das “ANKA-THz-Team”

The Team:

  • I. Birkel, T. Bückle❖, S. Casalbuoni, M. Fitterer,
  • B. Gasharova, E. Huttel, Y.-L. Mathis, D.A. Moss,

A.-S. Müller, M. Süpfle, P . Wesolowski Institut für Synchrotronstrahlung, Forschungszentrum Karlsruhe

❖Lab. f. Appl. d. Synchrotronstrahlung, Universität Karlsruhe (TH)

UVSOR, 24/9/2007 Short Bunches at ANKA page 2

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SLIDE 3

Outline

Operation with short bunches ➜ Beam energies ➜ SCU14 Beam studies ➜ Systematics of bunch length measurements with a Michelson interferometer Radiation characteristics ➜ Polarisation ➜ Development of bursts Summary & Perspectives

UVSOR, 24/9/2007 Short Bunches at ANKA page 3

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SLIDE 4

Research Centre Karlsruhe

Research & development in various fields:

environmental analysis medicine/bio technology material science microsystem technology (astro) particle physics IT science nano technology ...

UVSOR, 24/9/2007 Short Bunches at ANKA page 4

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SLIDE 5

The ANKA Storage Ring

✔ C = 110.4 m ✔ 0.5 ≤ E0 ≤ 2.5 GeV ✔ εx = 40 nm·rad ✔ DBA lattice

UVSOR, 24/9/2007 Short Bunches at ANKA page 5

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SLIDE 6

Low-αc Operation

Per year 12 days are dedicated short bunch operation for users as “special user operation”. Typical beam energy in this mode is 1.3 GeV ➜ longitudinal instability due to one higher order cavity mode for E0 < 1 GeV Low-α mode also operational at 1 GeV and 1.6 GeV on demand. In May 2007 a Helmholtz University Young Investigators Group dedica- ted to the study of the short bunch dynamics in storage rings has been founded.

F . Pérez et al., PAC03

UVSOR, 24/9/2007 Short Bunches at ANKA – Operation page 6

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SLIDE 7

SCU14 and Short Bunches

Short bunch operation for X-ray users at E0 = 1.3 GeV ➜ boost the photon energy with the SCU14 ➜ potential for time resolved experiments (∼ 106 integral photons/pulse)

  • A. Bernhard et al., “Performance of the First Superconducting Cold-Bore

Undulator in an Electron Storage Ring, PRSTAB 2006

UVSOR, 24/9/2007 Short Bunches at ANKA – Operation page 7

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SLIDE 8

Bunch Length and Beam Energy

The synchrotron tune is given by Q2

s =

αch 2πE e2 V2

RF − U2

A global fit yields an effective αc: αc = (6.6 ± 0.1) · 10−3 RDP at 2.5 GeV: (7.39 ± 0.01) · 10−3 The bunch length scales ∝ (E0)3/2 Calculate σs from fs with global αc “Low-αc squeeze” achieved for dif- ferent beam energies

fs / kHz Ebeam / MeV

VRF = 1.2 MV VRF = 0.6 MV Global Fit 20 40 60 1000 2000

σs / mm Ebeam / MeV

αc scan at 0.8 GeV αc scan at 1.0 GeV αc scan at 1.3 GeV αc scan at 1.6 GeV αc scan at 1.8 GeV from fit with VRF=0.6 MV from fit with VRF=1.2 MV 5 10 15 1000 2000

UVSOR, 24/9/2007 Short Bunches at ANKA – Operation page 8

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SLIDE 9

FIR-Spectrum & Beam Energy

0.5 1 1.5 10 20 30 40 50 60 70 80

Frequency [THz] Amplitude [a.u.]

E0 = 0.802 GeV, 0.21 mA E0 = 0.998 GeV, 0.47 mA E0 = 1.300 GeV, 0.43 mA E0 = 1.613 GeV, 0.27 mA

FIR spectrum for different beam energies (measured with a Michelson interferometer) Observations ➜ shift towards lower frequencies (longer bunches) with increasing E0 ➜ suppression of low frequency content for shorter bunches ➾ non-linearities of the detector? Observation of stable CSER also at 1.0 and 1.6 GeV.

UVSOR, 24/9/2007 Short Bunches at ANKA – Operation page 9

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SLIDE 10

Bunch Length from Interferograms

  • 1
  • 0.75
  • 0.5
  • 0.25

0.25 0.5 0.75 1

  • 5
  • 4
  • 3
  • 2
  • 1

1 2 3 4 5

Simplified view: wave train of frequency ω emitted by charge distribution of RMS length σ: A(t) = e

− “

1 2 t2 σ2 +iωt

”

The pulse overlayed with itself shifted by a time ∆ due to the Michelson interferometer is A(t, ∆) = e

− “

1 2 t2 σ2 +iωt

”

+ e

− „

1 2 (t+∆)2 σ2

+iω(t+∆) «

The time integrated intensity observed by the detector is therefore

˜

I(∆) =

  • I(∆)dt =
  • |A(∆)|2dt ∝

cos (ω∆) e−

∆2 4σ2

Assumption: Since the shortest wave length emitted coherently is equal to full bunch length λmin = 2σw, the max. frequency is ωmax = 2πc/λmin = πc/σw. It follows that

˜

I(∆) ∝

cos (ωmax∆) e−

∆2 4σ2 =

cos

π σ∆

  • e−

∆2 4σ2

➜ Exponential doesn’t change peak width: FWHM yields σ

UVSOR, 24/9/2007 Short Bunches at ANKA – Bunch Length Systematics page 10

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SLIDE 11

Background Subtraction

The coherent signal in the interferogram is superimposed by the incoherent and the thermal contributions ➜ The width of the central peak (i.e. the cos term) must be determined only after background subtraction ➜ FWHM is very sensitive to noise ➾ determine zero-crossings

Amplitude / A.U. Mirror Sweep Time / ps

E0 = 1.3 GeV raw data background signal

0.2 10 11 12 13 14 15 16 17 18 19 20

UVSOR, 24/9/2007 Short Bunches at ANKA – Bunch Length Systematics page 11

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SLIDE 12

Interferograms and Energy

Amplitude / A.U. Mirror Sweep Time / ps

E0 = 0.998 GeV fs = 12.4 kHz fs = 11.7 kHz fs = 10.2 kHz fs = 7.2 kHz

  • 0.2
  • 0.15
  • 0.1
  • 0.05

0.05 0.1 0.15 0.2 0.25 10 11 12 13 14 15 16 17 18 19 20

Amplitude / A.U. Mirror Sweep Time / ps

E0 = 1.3 GeV fs = 9.30 kHz fs = 8.00 kHz fs = 6.25 kHz fs = 3.60 kHz

  • 0.15
  • 0.1
  • 0.05

0.05 0.1 0.15 0.2 10 11 12 13 14 15 16 17 18 19 20

Amplitude / A.U. Mirror Sweep Time / ps

E0 = 1.6 GeV fs = 9.60 kHz fs = 8.60 kHz fs = 7.60 kHz fs = 6.40 kHz

  • 0.15
  • 0.1
  • 0.05

0.05 0.1 0.15 0.2 10 11 12 13 14 15 16 17 18 19 20

Background subtracted data for different beam energies and “squeeze states”: ➜ the higher the energy, the lower the noise ➜ cavity mode?

UVSOR, 24/9/2007 Short Bunches at ANKA – Bunch Length Systematics page 12

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SLIDE 13

Beam Splitter Comparison

Amplitude / A.U. Wave Number / cm-1

Hg lamp Bolo 4.2K, 2, 6 µm Si/Myl Bolo 4.2K, 2, 50 µm Myl Bolo 4.2K, 2, 125 µm Myl 2 4 6 8 10 12 10 20 30 40 50 60

Amplitude / A.U. Mirror Sweep Time / ps

Hg lamp Bolo 4.2K, 2, 6 µm Si/Myl Bolo 4.2K, 2, 50 µm Myl Bolo 4.2K, 2, 125 µm Myl

  • 0.2

0.2 0.4 0.6 0.8 1 10 11 12 13 14 15 16 17 18 19 20

Amplitude / A.U. Wave Number / cm-1

E0 = 1.3 GeV Bolo 4.2K, 2, 6 µm Si/Myl Bolo 4.2K, 2, 50 µm Myl Bolo 4.2K, 2, 125 µm Myl 10 20 30 40 50 60 70 10 20 30 40 50 60

Amplitude / A.U. Mirror Sweep Time / ps

E0 = 1.3 GeV Bolo 4.2K, 2, 6 µm Si/Myl Bolo 4.2K, 2, 50 µm Myl Bolo 4.2K, 2, 125 µm Myl

  • 0.2

0.2 0.4 0.6 0.8 1 10 11 12 13 14 15 16 17 18 19 20

UVSOR, 24/9/2007 Short Bunches at ANKA – Bunch Length Systematics page 13

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SLIDE 14

Bunch Length and Current I

Conclusion from beam splitter comparison: thin splitters are more sensitive in the critical region of the spectrum ➜ 6 µm Si/Mylar splitter expected to be more sensitive to small bunch length changes (e.g. due to beam current change) than 125 µm Mylar splitter

σs / ps Ibeam / mA

E0 = 1.3 GeV Bolo 4.2K, 2, 6 µm Si/Myl Bolo 4.2K, 2, 125 µm Myl

0.5 1 1.5 5 10

< σs >= (0.538 ± 0.008) ps

UVSOR, 24/9/2007 Short Bunches at ANKA – Bunch Length Systematics page 14

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SLIDE 15

Bunch Length and Current II

Observation of coherent emission for 2 π σs,real √

ln N

λobserved

  • r

σs,real √

ln N

π σs,observed Correct the σ derived from interferogram accordingly ➜ if the beam splitter is sensitive, the N dependence must vanish insensitive sensitive

σcorr / ps Ibeam / mA

E0 = 1.3 GeV Bolo 4.2K, 2, 6 µm Si/Myl Bolo 4.2K, 2, 125 µm Myl

1 1.5 2 5 10 15 20

< σs >= (0.787 ± 0.008) ps

UVSOR, 24/9/2007 Short Bunches at ANKA – Bunch Length Systematics page 15

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SLIDE 16

Bunch Length from Spectrum

Determination of σ from normalised spectrum Ideally normalisation by incoherent spectrum ➜ Problem: low intensity ➜ Alternative: Normalise by spectrum of Hg lamp The bunch length is related to the spectral bandwidth σk by (G. Wüstefeld, SBSR05): σs = 1 2 π √ 2 σk The bunch length determined thus is 0.375 ps.

(Pcoh / PHg) / a.u. Wave Number / cm-1

E0 = 1.3 GeV fs = 6.25 kHz Gaussian with σk=10cm-1

1 10 10 2 10 3 10 4 10

UVSOR, 24/9/2007 Short Bunches at ANKA – Bunch Length Systematics page 16

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SLIDE 17

Polarisation

0.2 0.4 0.6 0.8 1 1.2 10 20 30 40 50 60 70 80

Frequency [THz] Amplitude [a.u.]

Polarizer at 0o Polarizer at 30o Polarizer at 60o Polarizer at 90o 30 60 90 120 150 180 0.5 1 1.5 2

Polarizer Orientation in Deg Amplitude [a.u.]

0.2 0.4 0.6 0.8 1 1.2 0.75 0.8 0.85 0.9 0.95 1

Frequency [THz] (Pmax−Pmin) / (Pmax+Pmin) E0 = 1.3 GeV fs = 6.0 kHz

Edge radiation in mid-IR shows radial polarisation For very low frequencies only a slice of the radiation in the orbit plane is visible ➜ measure mostly linear polarisation

✔

UVSOR, 24/9/2007 Short Bunches at ANKA – Radiation Characteristics page 17

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SLIDE 18

Bursting Emission

amplitude / mV time / s

  • 0.3
  • 0.25
  • 0.2
  • 0.15
  • 0.1
  • 0.05

0.05

  • 0.04
  • 0.02

0.02 0.04

Investigate the frequency content time slice by time slice

UVSOR, 24/9/2007 Short Bunches at ANKA – Radiation Characteristics page 18

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SLIDE 19

Zooming into a Burst

2000 4000 6000 −0.05 0.05 0.2 0.4 0.6 0.8 1

Frequency (Hz)

Time (sec) LNP

2000 4000 6000 −0.05 0.05 0.5 1 1.5 2 2.5 3 3.5 Frequency (Hz) Time (sec) LNP

Study of the change of the bolometer signal frequency contents during the build-up of a burst ➜ signal around a burst is cut in slices that are analysed separately High current: double peak structure around fs (σs oscillations?) Low current: fs structure gone and

  • max. of burst more pronounced

Ibunch = 0.47mA Ibunch = 0.16mA

UVSOR, 24/9/2007 Short Bunches at ANKA – Radiation Characteristics page 19

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SLIDE 20

Perspectives

Accelerator : ➜ A dual sweep streak camera will be added to the ANKA diagnostics for direct bunch length measurements ➜ A single bunch gun will replace the present diode gun for systematic studies of single bunch / multi-bunch differences ➜ HEB to resolve revolution Experiments: ➜ Time resolved measurements making use of the short X-ray pulses generated in the SCU14

UVSOR, 24/9/2007 Short Bunches at ANKA – Radiation Characteristics page 20

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SLIDE 21

Summary

Regular low-αc mode for special user operation at 1.3 GeV Potential for X-ray experiments using the SCU 14 Beam studies: ➜ Extensive and ongoing study of bunch length measurements systematics ➜ Investigation of radiation properties ➜ Further instrumentation will allow a closer look

UVSOR, 24/9/2007 Short Bunches at ANKA – Radiation Characteristics page 21

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SLIDE 22

Bunch Length from Spectrum

(Pcoh / Pincoh) Wave Number / cm-1

E0 = 1.3 GeV fs = 6.25 kHz Gaussian with σk=10cm-1

1 10 10 2 10 3 10 4 10

UVSOR, 24/9/2007 Short Bunches at ANKA – Radiation Characteristics page 22