Beschleunigerphysikalische Herausforderungen an PETRA 3

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Beschleunigerphysikalische Herausforderungen an
PETRA 3

• Grömitz, September 2004
• Winni Decking, DESY-MPY
• Das PETRA Design Team
• Klaus Balewski
• Werner Brefeld
• Winni Decking
• Yongjun Li
• Gajendra K. Sahoo
• Rainer Wanzenberg

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Outline

• Einleitung Parameter
• Die 3 Herasuforderungen
• 1. Kleine Emittanzen
• Lattice Optionen
• Dynamische Apertur
• Strahldynamik mit Wigglern
• 2. Stabiler Orbit gt Poster, F. Brinkers Vortrag
• 3. Hoher Strom gt Poster, R.Wanzenbergs Vortrag

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The Brilliance (Brightness) Gap

• Closing the gap between the high-flux/low
  brightness source DORIS III and the
  high-brightness X-FEL
• A high-brightness ring based source
• Balance between brightness and photon energy
• Not to expensive
• To be constructed in reasonable time
• With the end of the HEP program at HERA the
  injector PETRA II becomes available

Average brilliance 1. BESSY II U125, 2. ALS U5,
3. DIAMOND U46, 4. ESRF ID16, 5. SPring-8 BL46
PETRA III a. soft-X-ray undulator (4 m, high-),
b. standard Kmax 2.2 undulator (5 m, high-), c.
hard X-ray wiggler (Kmax 7, 5 m, high-).
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PETRA III Parameter
Design specifications cost effective ()
competitive with high
energy SR sources
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PETRA III
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New Octant DBA Cell

• Design requirements (users)
• 5 m long insertion device
• low and high bx
• Design constrains (machine)
• low ?, low e
• Design consequences
• Dx small gt no sextupoles
• Beam sizes at ID positions
• Horizontal 35-150 mm
• Vertical 5 mm

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Emittance Constituents
Optics
Ring Geometry
Given by user constraints

• For small emittance you need
• Large bending radius
• Small bending angle per cell
• Small horizontal beta-functions

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Old Octant Cell Options

• 90o short FODO cell
• Lattice and hardware new
• Small dispersion, strong focusing leads to strong
  chromatic sextupoles

• TME cell
• Lattice new
• Hardware reused
• Small dispersion, strong focusing leads to strong
  chromatic sextupoles

• 72o FODO cell
• Lattice unchanged
• Damping wiggler needed to reach 1nmrad

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Wiggler Requirements
depends on wiggler field shape

• Total field integral
• ?B2m ? 98 T2m
• Maximum field and period length
• B3l2 ? 0.2

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PETRA 3 Damping Wigglers
Period 20 cm Field
amplitude 1.56 T Field quality _at_ 1 cm
lt10-3 Total length 80 m Total radiation
power 887 kW
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Beam Dynamics with Wigglers

• Wigglers have strongly varying field along
  longitudinal axis
• Most effects cancel after one period
• But Some perturbations are always in phase with
  the sinusoidal particle motion and add up
• Need to integrate particle motion along
  longitudinal axis
• DIFFICULT

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Wiggler Field Calculations
Longitudinales Feldprofil

• Wiggler Design (Novosibirsk)
• l0.2m
• B1.56 T

Halbach Formulae
Transversales Feldprofil
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Particle Motion in Wiggler Field
4th order Hamiltonian of planar Wiggler
Cancel after one period
Dont cancel after one period
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Particle Tracking

• Runge Kutta Integration through
  measured/calculated field maps
• Taylor map expansion
• Symplectify Taylor map with generating function
• Symplectic Integration through fitted field maps
• Integrate Hamiltonian

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Phase Space without/with Wiggler
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Aperture
Physical
Dynamic
RF
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Comparison of lattices (1)
Short FODO 90
FODO 72
TME
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Comparison of lattices (2)

• Dynamic Aperture for injection
• big beam has to fit into the machine

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Comparison of lattices (3)

• Dynamic Aperture for lifetime
• scattered particles have to stay in the machine

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Wiggler and Undulator
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Dynamic Aperture with/without all insertion
devices
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Beam Lifetime
Gas Scattering with 1?10-9 mbar at 200 mA and
1?10-10 mbar base pressure Touschek Lifetime for
1 coupling
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Finding the golden orbit (1)
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Finding the golden orbit (2)
Combined orbit dispersion correction
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Ground Motion at various Accelerator Sites
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Fast Orbit Motion at PETRA II
FFT
0.1 sx14mm
0.1 sy
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Successive Fast Correction

• Using all monitors
• Fast correctors in the new octant 2 fast
  correctors in each straight

Simulation using additional 1 mm RMS random
offset at quads
Emittance and stability goal achieved
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Summary

• PETRA 3 schließt die Lücke zwischen DORIS III und
  existierenden 3te Generations-Synchrotronlichtquel
  len
• Idealer Partner für das X-FEL Project
• (Ideales Testfeld für LC Dämpfungsringe)
• Spannende Beschleunigerphysik, die uns
  hoffentlich noch so manchen Grund für ein
  Betriebsseminar liefert

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Current limitations (1)

• Single bunch instabilities
• PETRA II no evidence for single bunch
  instabilities up to currents of 10 mA
• Impedance 16 7-cell cavities vacuum chamber
  joints, IB2.5 mA leads to theoretical tune
  shifts

• PETRA III
• 1) new vacuum chamber in old octants impedance
  should not get worse
• 2) vacuum chamber new octant significant (up to
  factor 2) increase of transverse impedance
• gt still 2.5 mA single bunch current should be
  O.K.

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Current limitations (2)

• Multibunch instabilities
• Present situation PETRA II (measured threshold
  and damping)

PETRA III 12 instead of 16 cav. larger long.
(radiation) damping
? powerful broadband (BW 60MHz) feedback
necessary
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Current limitations (3)

• Electrons vs. Positrons

electrons eases operation of LINAC -
ions dust PETRA II no ions but dust
positrons no ion or dust problems - more
difficult operation of LINAC
e-cloud is ok
DORIS III operation requires positrons!! As long
as DORIS III is running PETRA III will be
operated with positrons