UMER : The University of Maryland Electron Storage Ring

Transcription

1 UMER : The University of Maryland Electron Storage Ring Rami A. Kishek on behalf of UMER collaboration Institute for Research in Electronics & Applied Physics University of Maryland, College Park, MD Research sponsored by US Department of Energy

2 We Thank: University of Maryland Electron Ring (UMER) Team: Patrick O Shea Martin Reiser Irving Haber Rami Kishek Terry F. Godlove Don Feldman Renee Feldman Junior Scientists: Santiago Bernal Mark Walter Bryan Quinn Graduate: John Harris Gang Bai Kai Tian Mike Holloway C Papadopoulos Diktys Stratakis Former: Yun Zou Yupeng Cui Hui Li Yijie Huo Charles Tobin Virtual National Lab for Heavy Ion Fusion (also provided WARP) NIU Alex Friedman Dave Grote Jean-Luc Vay John Barnard Court Bohn Peter Seidel Christine Celata Steve Lund Simon Yu Ioannis Sideris PPPL Ron Davidson Hong Qin Eric Gilson Others Ingo Hoffman Tom Wangler

3 Outline 1. The University of Maryland Electron Ring: Why and What? 2. UMER Design 3. Transverse Physics and Control 4. Longitudinal Physics 5. Summary

4 Why electrons? Scaling Laws E+12 1 kev 1 MeV 1 GeV 1 TeV e - electrons p protons HI heavy ions UMER

5 Common Beam Dynamics Challenges Transverse: Errors & Control Halo Formation & Beam Losses Emittance Growth Instabilities Resonances Longitudinal: Energy Spread Transverse-Longitudinal Coupling Compression Instabilities

6 UMER Schematic Injection/ matching section 10 kv Gun Extraction/ diagnostic section 3.7 m

7 UMER is a Complex Machine Electron Gun Injection Line Ring Chambers Diagnostic Chamber > 150 Magnets Assembly, Alignment Power Supplies, Wiring Diagnostics Beam Control

8 UMER as of Aug. 2004

9 Review of UMER Design

10 UMER Beams Energy Energy Spread Current Range rms Emittance n Range 10 kev 20 ev ma µm Non-Relativistic: Negligible radiation, below transition, etc. Earth field important! Low Energy Spread Current and Emittance Adjustable: using apertures in the gun (large jumps) by varying the gun grid voltage (fine-tuning)

11 Dimensionless Space Charge Intensity Intensity Parameter: χ K = ka 2 2 o space charge force external focusing force 0 c 1 2a Beam external focusing K a k 0 2 a ε + a 2 3 Space charge + emittance

12 Existing rings Present UMER Operating Points Emittance Dominated UMER Range 0.6 ma Space-charge Dominated Plasma Oscillations Curve ω P ω = 0 2χ Beams Circulated ma ma 85 ma Intensity Parameter (c) Betatron Oscillations Curve ω 1 ω = χ 0

13 UMER Lattice Parameters Ring Circumference Ring Radius Lattice Period Number Lattice Periods Zero-Current Tune Zero-Current Tune Range Average Beam Radius m 1.83 m 32 cm 36/turn mm Tune adjustable, currently 3 operating points Interested also in anisotropic focusing (different tunes in x and y)

14 PC Dipoles (34 X) Dipole field Current Physical length Effective length Radius Field integral Resistance UMER Magnets & Lattice 15.4 G 3 A 4.4 cm 3.8 cm 2.8 cm 20 G-cm/A 3 Ω PC Quadrupoles (68x) Field gradient ~ 8 G/cm Current 2 A Physical length 4.4 cm Effective length 3.6 cm Radius 2.8 cm Field integral 15 G/A Resistance 3 Ω

15 UMER Goals 1. Maintain emittance growth ε/ε < 4, while: At full current, without acceleration, 10 turns At lower current or with acceleration, 100 turns 2. Conduct a wide range of beam dynamics experiments on UMER!

16 Diagnostics Presently Installed Invasive (can only be used over first turn): Phosphor screen imagers: Beam-intensity image, size, position, and skew angle Beam emittance and transverse phase space (in combination with a quad scan and Tomographic techniques) Beam emittance (in combination with quincunx mask at gun) Non-Invasive (multi-turn diagnostics): Beam Position Monitors: Beam position Beam current Bergoz Coils (Beam Current) Perturbation Techniques (Line Charge)

17 Diagnostics to be Added 1. Energy Analyzers (invasive, can be placed in any chamber) 2. End Diagnostic Chamber (non-invasive): Time resolved high-resolution Energy Analyzer Slit-slit time-resolved transverse phase space mapper Pepper-pot transverse-phase-space mapper Current measurement devices Phosphor Screen Imager

18 Quadrupole Linearity & Field Profile 3-D field calculations: Z-integrals used for field quality. Constant k adjusted for best uniformity (dipole) or linearity (quad); e.g., k = for ring dipole; deviations <0.1%

19 Magnet Harmonic Measurements Rotating coil and pulsed wire systems Normal Multipole Harmonics Expected (w/ errors) Quadrupole 10 4 Sextupole 20 Octupole 68 Decapole 13 Duodecapole 130 Allowed Max Zhang, et al., PRST-AB, 3, (2000). Measured

20 Injector New Injection Y in place IQF SD Big DCQ PD RQ1 SD Ring

21 Beam Control

22 First Experiments (during construction) Rotated Beam 24 ma, 10 kev 1.0 m RMS Mismatched S. Bernal (PAC 03) 1.0 cm

23 Beam Control System Software Quadrupoles Control Central Control Platform network Hui Li Dipoles Control network BPMs Control network Steering Module Skew Correction Module Matching Module Tomography Module

24 Beam Steering Screen/BPM D1 D2 Q1 Q2 I2(A) candidate candidate optimal point Steps: Scan Q1, find all rays through Q1 s center Scan Q2, find the optimal ray I1(A)

25 Beam Steering Results B-field (Gauss) Dipole Field (G) Scaled BEz (G) NET Field (G) Measured B z of Earth Field Dipole fields calculated w/ the steering algorithm Rough Scaled Sum of Earth and Dipole Fields Angle (degrees) Two pilot beams (7mA, 0.6mA) have given similar results.

26 Beam Rotation Correction Electronic Skew Corrector

27 Beam Rotation Correction 24mA Beam (RC1-12) Before Skew Correction 24mA Beam (RC1-12) After Skew Correction

28 Beam Rotation Correction 24mA Beam (RC1-12) Rotation Angle Before Correction v.s After Correction Beam Rotation Angle (degree) Chamber Index (RC1 to RC12) Skew = 0A Skew = 0.13A Skew corrector at here

29 Beam Matching 24mA Beam (RC1-12) after Skew Correction 24mA beam pictures (RC 1-12) after beam-based matching

30 Beam Matching Before empirical matching: σ x =0.20mm σ y =0.18mm After empirical matching: σ x =0.08mm σ y =0.04mm 9 8 Before Empirical matching, Var(x)=0.2002mm, Var(y)=0.1813mm X-2*rms size Y-2*rms size 9 8 After Empirical matching, Var(x)=0.0784mm, Var(y)=0.0438mm X-2*rms size Y-2*rms size 7 7 2*rms beam size (mm) *rms beam size (mm) Chamber # Chamber #

31 Longitudinal Dynamics: Inducing Perturbations

32 Photo & Thermionic Emission Electron Beams Electron Beam Beam Current Heated Photocathode Thermionic only, 100ns pulse Drive Laser Photoemission + Thermionic 5ns pulse Photoemission only (Cool cathode) Yijie Huo

33 Drive Laser Setup Laser Mask Telescope Mirrors /filters BBO KTP UV (355nm) Laser Photon energy: 3.5 ev Work function: 2.7 ev Nd:YAG Laser

34 Experiment Data Positions IC1 Window : IC m Laser IC2 RC1 RC2 RC3 Bergoz Coil BPM : IC2 BPM : RC1 BPM : RC2 BPM : RC3 BPM : RC4 BPM : RC5 BPM : RC6 BPM : RC7 BPM : RC8 BPM : RC9 BPM : RC10 BPM : RC11 BPM : RC m 0.80 m 1.91 m 2.55 m 3.19 m 3.83 m 4.47 m 5.11 m 5.75 m 6.39 m 7.03 m 7.67 m 8.31 m 8.95 m 4 5 RC

35 Conclusion UMER Mechanically Closed Beam Control algorithms and systems developed. Poised for Multi-Turn Operation Can use laser to produce localized density perturbations good agreement with WARP simulations. Rich physics content promises exciting results Website: Publications:

36 Extras

37 Design of Printed Circuit Magnets 10 kev use ironless printed-circuit magnets Quadrupole, Dipoles, and additional Short Dipoles for small steering corrections Can handle up to 3 Amps DC/conductor. Double-sided: minimizes effect of external leads & doubles the field. Algorithm: sin(mf n ) = 1 - (2z n /kl) 2, n = 20 loops for ring dipoles (m=1) and quad s (m=2) Courtesy of T.F. Godlove

38 FFT of Rotating Coil Signal FFT of Rotating Coil Signal (dbm) NO MAGNET Frequency (Hz) FFT of Rotating Coil Signal (dbm) PC DIPOLE Frequency (Hz) FFT of Rotating Coil Signal (dbm) PC QUADRUPOLE Frequency (Hz)

39 Sources of Quad Multipole Spectrum H V R