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Beam Physics Department

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Beam Physics Department Yunhai Cai DOE Program Review, SLAC June 13, 2007 Members in Beam Physics Department Professors: Alex Chao Ron Ruth Post-doctor: Yuantao Ding ... – PowerPoint PPT presentation

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Title: Beam Physics Department


1
Beam Physics Department
  • Yunhai Cai
  • DOE Program Review, SLAC
  • June 13, 2007

2
Members in Beam Physics Department
  • Professors
  • Alex Chao
  • Ron Ruth
  • Post-doctor
  • Yuantao Ding
  • Students
  • Daniel Ratner
  • Jerry Wang
  • Administrative
  • Tom Knight
  • Margie Bangali
  • Head
  • Yunhai Cai
  • Staff
  • Gennady Stupakov
  • Sam Heifets
  • Karl Bane
  • Zhirong Huang
  • Yiton Yan
  • Yuri Nosochkov
  • Min-Huey Wang
  • Associates
  • Bob Warnock
  • Martin Lee
  • John Irwin

3
Accounts Charged for the Activities
  • 50 accelerator research beam dynamics and
    instabilities, FEL physics
  • 50 program support PEP-II, ILC, LCLS, SEBAR
  • Year 20062007, published 67 papers among them
    16 on peer-reviewed journals

4
Core Competencies in Beam Physics Department
  • Lattice design and single-particle beam dynamics
    in storage rings
  • Designed optics for PEP-II, SABER, SPEAR3
    upgrades, ILC
  • Accelerator modeling and improvement, PEP-II
  • Wakefield and impedance, collective effects and
    instabilities of intensely charged beam
  • Impedance at very high frequency
  • Coherent synchrotron radiation and its dynamical
    effects
  • Physics related to ultra-short bunches
  • Beam-beam effects in the colliders
  • Simulation and parallel computing
  • Lie-algebra-based linear and nonlinear analysis
    codes LEGO and Zlib
  • PIC simulation of beam-beam interaction and
    luminosity BBI
  • Nonlinear Vlasov solver for microwave instability
  • Theory of free-electron laser
  • Regenerative Amplifier FEL
  • Teach at Stanford University and US Particle
    Accelerator School
  • Single-particle dynamics, FEL physics, impedance
    and instabilities

5
Improvements of Online Model
VAX SCP database R-Matrix Or
Twiss steering package beta measurement
Linux PEP-II optics Optics codes MAD DIMAD LEGO
AT Model codes MIA
buffer data
  • Parameters in optics model are used as inputs of
    beam-beam simulation
  • to figure out what to do as the next step.
  • Several computer programs are developed to
    correct optics, such as
  • beta beating, dispersion, and coupling.

6
Comparison Between Measurement and Calculation
Based of Beam-Based Online Model
nx
ny
x-oscillation
dispersions
7
Predictive Power of Precision Model Nonlinear
Beam Dynamics
  • Measured chromatic optics and dynamic aperture in
    HER
  • Excellent agreement between measurements and LEGO
    model in the chromatic optics
  • Improvement of understanding of nonlinear
    dynamics including sextupoles

8
Developed Accurate Online and Offline Models
Comparison of quadrupole strength between LER
model and configuration, May 30, 2007
9
Improvement of Machine Optics and Luminosity for
PEP-II
Achieved peak luminosity 1.2x1034cm-2s-1, August
15, 2006
10
An Alternative Approach to Double the Luminosity
Without Increase Beam Currents
  • Beam-beam codes were benchmarked against our
    KEKB colleagues and
  • many measurement. Simulations show a
    significant increase of luminosity
  • as coupling decreases in both machine.
  • Some skew quadrupoles are necessary to reduce
    the design vertical
  • emittance. Extensive tuning and MD may be
    necessary as well.

11
LER lattice with low vertical emittance
The new IR local coupling correction is
implemented. It uses 12 additional permanent skew
quads (PSK) to reduce the design vertical
emittance from 0.50 nm to 0.034 nm.
SK5,6L
SK5,6
The main source of emittance in the design
lattice is the local coupling and dispersion from
SK5,6 skew quads on left/right sides of IR.
old
5 PSK
7 PSK
In the new solution, the IR coupling is better
localized by setting the strengths of SK5,6 to
zero, and including the 12 PSK quads closer to
IP. Their positions and strengths are optimized
for minimum vertical emittance.
new
IP
12
Mode Emittances in the PEP-II Rings after the PSK
lattice was implemented into the LER
May 30, 2007 models. At this moment, luminosity
is 10 below the best achieved value at currents
of 2450/1775 mA.
13
14 mrad ILC extraction line
The ILC single IR optics is re-designed to allow
a fast interchange between two different
detectors and different L (push-pull detector
option).
Redesigned extraction optics with energy and
polarimeter diagnostics, and the 2nd beam focus.
Detector dependent optics
Fixed optics
Fast x-y kickers sweep the beam on 3 cm circle at
the dump to reduce power density and prevent
water boiling in the dump vessel.
Disrupted large energy spread leads to low energy
losses.
X
collimators
magnets
Y
14
Impedance Instabilities in the ILC Damping Rings
  • A working group from several departments PBD,
    ACD, ASD
  • Develop an impedance model and estimate threshold
    of instabilities, in particular, microwave
    instability, which may has impact of choice of
    momentum compaction factor for the damping rings.

15
RESISTIVE WALL IMPEDANCE OF A SURFACE WITH
TRIANGULAR GROOVES
A surface with triangular grooves can
significantly reduce the secondary emission yield
below the multipacting threshold with weak
dependence on the size of surface and magnetic
field.
Electric field lines in the groove.
Impedance amplification factor as a function of
the angle.
16
Optimization of ILC Linac RF Distribution System
-As an example Overall P and Individual
Q Adjustments
For p 0.92, tb 0.89, gradient at head and tail
of train
  • One seed
  • Red dots give (glim)I
  • Loss only 3
  • compare to 20 in
  • the worst case

17
SABER final focus
SABER final focus is redesigned for using
existing SLAC spare quadrupoles from SLC and
FFTB. Round beam at IP with E 28.5 GeV, bx
1.5 cm, by 15 cm, hx,y 0.
IP
W/o bypass sx 6.9 mm, sy 6.7 mm, sz 18.8
mm.
With bypass sx 5.5 mm, sy 6.1 mm, sz 19.3
mm.
18
Orbit Response of Horizontal Kick q in Strongly
Coupled Lattices
General solution of closed orbit
Rab
Ab
b
Aa-1
Mab
a
a
19
Emittance exchange
  • Natural beam configuration of RF gun not
    optimal for FEL transverse emittances too large,
    intrinsic E-spread too small
  • Better beam configuration obtainable through 6D
    phase space manipulation (flat beam gun x-z
    emittance exchange)
  • Very small transverse emittances achieved in
    simulations
  • for 20 pC charge, ??x 0.16 ?m
  • ??y 0.0054 ?m
  • ??z 11 ?m

k
dipole
deflecting cavity
Emma, Huang, Kim, Piot, PRSTAB 9, 100702 (2006)
20
HIGH FREQUENCY IMPEDANCE CALCULATIONS
A theory of high frequency impedance is developed
for various non-axisymmetric geometries such as
irises/short collimators in a beam pipe, step-in
transitions, step-out transitions, and more
complicated transitions of practical Importance
G. Stupakov, K. Bane, Zagrodnov, PRSTAB 10,
054401 (2007) .
For a flat iris with aperture 2g in a flat beam
pipe of aperture 2b, the transverse impedances as
functions of g/b.
21
MICROWAY INSTABILITY STUDIES FOR THE ILC DR
A new computer code is developed that solves a
linearized Vlasov equation in the time domain.
The code is implemented in Mathematica it can be
easily modified and augmented.
Growth rate for the CSR induced microwave
instability as a function of current.
Phase space of the microwave instability.
22
Bunch Lengthening Variation along Bunch Train
Due to RF Gap Transient
Transient PWD
gap transients only
  • Measured by Novokhatski
  • Figures on right show calculated variation of
    bunch length at different currents (shown in Amp)

S. Heifets, S. Novokhatski, D. Teytelman,
PRSTAB 10, 011001, (2007).
23
Ultra-Low Emittance Ring with FEL
  • A lattice with 0.1 nm-rad emittance at 7.0 Gev
    and 0.05 nm-rad at 4.5 Gev.
  • Steady-state SASE
  • wavelength 5-100nm, pulse length 10 ps, rep rate
    100 kHz, peak power 1MW, undulator length
    100m
  • HHG seeding1MW, 10 fs at
  • 10 nm, 10 m modulatorchicane
  • HGHG FEL output at 3.3 nm

5 nm SASE
24
LARP Beam-Beam Workshop for LHC (at SLAC) LARP Beam-Beam Workshop for LHC (at SLAC) LARP Beam-Beam Workshop for LHC (at SLAC) LARP Beam-Beam Workshop for LHC (at SLAC) LARP Beam-Beam Workshop for LHC (at SLAC)
900 3510 min F. Zimmermann, CERN F. Zimmermann, CERN LHC expected beam-beam performance for nominal and upgrade parameters
945 3510 min K. Ohmi, KEK K. Ohmi, KEK B-Factories beam-beam performance
Morning II - Machines performances Morning II - Machines performances Morning II - Machines performances Morning II - Machines performances Morning II - Machines performances
1045 3510 min A. Valishev, FNAL Tevatron beam-beam phenomena and counter-measures Tevatron beam-beam phenomena and counter-measures
1130 3510 min W. Fischer/C. Montag, BNL RHIC beam-beam performance RHIC beam-beam performance
Afternoon I - General simulations Afternoon I - General simulations Afternoon I - General simulations Afternoon I - General simulations Afternoon I - General simulations
130 2010 min A. Kabel, SLAC What can be predicted with beam-beam simulations in hadron machines What can be predicted with beam-beam simulations in hadron machines
200 2010 min A. Valishev, FNAL Simulations that explain and predict beam-beam effects in the Tevatron Simulations that explain and predict beam-beam effects in the Tevatron
230 2010 min J. Qiang, LBNL Beam-beam simulations for RHIC and LHC Beam-beam simulations for RHIC and LHC
Afternoon II - New operating modes, theory, unexplained observations Afternoon II - New operating modes, theory, unexplained observations Afternoon II - New operating modes, theory, unexplained observations Afternoon II - New operating modes, theory, unexplained observations Afternoon II - New operating modes, theory, unexplained observations
345 2010 min K. Ohmi, KEK Experience with crab cavity operation in KEKB Experience with crab cavity operation in KEKB
415 2010 min Y. Alexahin, FNAL Theory and reality of coherent effects in Tevatron, RHIC, and LHC Theory and reality of coherent effects in Tevatron, RHIC, and LHC
445 2010 min Y. Cai, SLAC Unexplained phenomena in lepton machines Unexplained phenomena in lepton machines
Tuesday, 3 July 2007 Tuesday, 3 July 2007 Tuesday, 3 July 2007 Tuesday, 3 July 2007 Tuesday, 3 July 2007
25
Conclusion
  • BPD has made significant contribution to the
    success for the PEP-II operation in the past year
    as many long-term research activities baring
    their fruits, most noticeable beam-beam
    simulation and precision optics modeling.
  • We continued to important contributes to
    accelerator projects ILC, SABER, LCLS, and
    future possibilities SuperB and 5th generation
    light source.
  • We published many accelerator research papers on
    peer-reviewed journals and continued to teach at
    Stanford University and USPAS.
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