Beam Emittance Measurements at Fermilab – Experience at Run II and Plans for Project X –

1. Beam Emittance Measurementsat Fermilab– Experience at Run II and Plans for Project X – Manfred Wendt Fermilab Many thanks for contributions from:Sam Childress, Nathan Eddy, Martin Hu, Vic Scarpine, Mike Syphers, Gianni Tassotto, Randy Thurman-Keup, Ming-Jen Yang, Jim Zagel, and others. ABI Workshop on Emittance Measurements

2. Outline • Introduction • Examples of Run II Emittance Diagnostics • Transverse Monitors: • Flying wire [Tevatron] • Ionization profile monitor (IPM) [Tevatron] • Synchrotron light monitor [Tevatron] • Multi-wire (harp) [MI, NuMI Beam-lines (8 & 120 GeV)] • Optical transition radiation (OTR) screen [MuMI Beam-line 120 GeV] • Schottky detector [Recycler] • Longitudinal Monitor: • Wall current monitor (WCM) & fast oscilloscope [Tevatron] • Fermilab’s Future: Project X? • Challenges on Emittance Diagnostics • Laser wire collaboration ABI Workshop on Emittance Measurements

3. Single Particle Tr. Emittance • Single particle motion*: • Courant-Snyder invariant:(transverse emittance) • Twiss parameters: x(s) x’ x s x’ : Envelope function x ε [π mm mRad] *linear elements ABI Workshop on Emittance Measurements

4. Emittance (Gaussian Distr.) • Fermilab emittance definition:x–x’ phase space area occupied by 95 % of particles • Assume Gaussian stationary density distribution • Circles in x–(αx+βx’) phase space • Emittance for Gaussian Distribution: • F=0.95 (95 %) transverse normalizedemittance in presence of dispersion D: • β Betatron and D dispersion lattice parameters • transverse(σ) and longitudinal (dp/P) profile measurements x – x’ phase space with: x-axis projection(beam profile) ABI Workshop on Emittance Measurements

5. Accelerators at Fermilab NuMI: 320 kW beam power Main Injector: 3x1013 protons/pulse @ 120 GeV (2.2 sec) Tevatron: 1x1013 protons, 3x1012 pbar980 GeV ABI Workshop on Emittance Measurements

6. Flying Wire Monitor • Wire: 5 µm carbon • Speed: 6.6 m/sec • Max. beam intensity: < 3x1013 p (NuMI) Scraping Losses (TeV) TeV Flying Wire installation at locationE11 ABI Workshop on Emittance Measurements

7. 7µm Flying Wire Clamp ABI Workshop on Emittance Measurements

8. TeV εTfrom Flying Wires E17H Open Helix Ramp location E17: high dispersion P/P E11V location E11: low dispersion E11H ABI Workshop on Emittance Measurements

9. Notes to the Measurements • Expect the emittance to be ~constant from injection to flattop • Real world beam-beam, vacuum, etc. causes slight emittance growth. • E17H (high D) should be the same as E11H (low D) • Error believe to be due to D, b • Makes solving for p/P a very poor technique • Observe clear shifts in emittance when machine state changes (open helix, ramp) • Suggests D, b are changing • See largest accuracy issues in H -> D issues • To first order, D=0 in vertical and it behaves the best • Change in εV after ramp must be due to error in b • The accuracy of the momentum spread is believed to be very good, measured with the WCM / fast oscilloscope. • Operationally, the E11H measurement is believed to be the most accurate • Best behaved from injection to 980 GeV • Expect round beam, i.e. εV = εH ABI Workshop on Emittance Measurements

10. Some Remarks • The Instrumentation department provides precision measurements of the transverse & longitudinal profiles • The accuracy of the emittance measurement is dominated by the measurements of the lattice parameters • The accuracy of the measurements did not become a large concern until the operations department started doing their own calculation of the expected luminosity. ABI Workshop on Emittance Measurements

11. IPM vs. Flying Wire • Beam Intensity of 1011 particles per bunch at 10-9 torr. • But, good measurements of all pBar bunches(1010), with local gas bump of 10-8 torr. Comparison of TeV Flying Wire and IPM Measurements of Beam Size ABI Workshop on Emittance Measurements

12. TeV Synclight Monitor Pickoff Mirrors Protons Antiprotons Proton Box Half-Dipole Dipole Dipole Antiproton Box Proton light source Antiproton light sources • Synchrotron Radiation from the edges of Tevatron dipole magnets is intercepted by mirrors and imaged onto gated/intensified cameras (only at 980 GeV) • The beam sizes are corrected for • Camera non-linearities • Multiple sources (pbar only) • Diffraction (s ~ 100-200mm) • The emittance is calculated from • Beam size (s ~ 200-800mm) • Lattice parameters • Momentum spread (from longitudinal profile device) Antiproton Beam Image (smaller beam size and less optical magnification) ProtonBeamProjections Proton Beam Image ABI Workshop on Emittance Measurements

13. Longitudinal ε Measurement 8 core Intel Power Mac Tunnel TCP/IP Lecroy 6200 Scope Parallel Port Heliax Trigger Generator Parallel Port RWCM Trig Out Splitter Service Bldg Beam Trigger Longitudinal beam parameters are measured using a wall current monitor (WCM) that is digitized by a Lecroy Oscilloscope which is in turn read by a LabVIEW program. Timing is provided by custom boards. ABI Workshop on Emittance Measurements

14. Theory (without math) • Particles follow trajectories in phase space that are solutions of: • Experimentally, what is measured is the time distribution of the beam which is the projection of phase space onto the time axis. • To reconstruct phase space, one can use the time-axis projections of each contour ring as a set of fitting functions • Assumption is that the particle density around any annulus is constant • Fit the intensity vs. time distribution from the wall current monitor • Given the particle count in each contour, the emittance can be calculated, as well as the momentum spread Projection ABI Workshop on Emittance Measurements

15. Issues • Beam in the Tevatron is quite uniform since it circulates for long periods of time • Beam in the Main Injector is much less uniform due to the many RF manipulations that happen • Averaging can remove some of the non-uniformity • e.g. averaging traces taken over a synchrotron period Tevatron Tevatron is very uniform Remnants of coalescing during proton injections to the Tevatron Main Injector ABI Workshop on Emittance Measurements

16. Operational Aspect 10 5 Emittance (eV-s) dp/p (10-4) 0 0 0 22 Time (Hrs) Tevatron Store (plot of logged data) • Measurements are performed continuously • ~ 1 Hz in the Tevatron • ~ Every cycle in the Main Injector (~2-6 seconds per cycle depending on cycle type) • Measurements are logged Main Injector longitudinal profiles seen by operations personnel ABI Workshop on Emittance Measurements

17. Multiwire (or SEM) • FNAL type • Wire: 25 µm Ti (before W/Au) • Ceramic substrate, w beam gap, wires epoxied to pads. • University of Texas type • Signal planes: 5 µm Ti strips • Bias planes: 2.5 µm Ti foil • NuMI beam • Energy: 120 GeV • Intensity/pulse: 3x1013 protons • Beam time: 8.56 µsec / 2.2 sec • Power/spill: 140 kJoule • Σ total: > 3x1020 protons • Extrapolation • 5 µm Ti strip (1660 degC – 10 %): ~1.6x1014 protons (max) thermal simulation 5 µm strip, 3x1013 p FNAL Assembly University of Texas SEM ABI Workshop on Emittance Measurements

18. MI 8 GeV Beam-line • Normalized emittance (1 σ): • σi: measured profile at i-location • σp: computed momentum width • βi: beta function at i-location • Di: dispersion function at i-location • ε: Emittance, in π-mm-mRad • (βγ)rel: relativistic beta-gamma • H and 2: calculated by solving a set of 2x2 simultaneous equations. • V is calculated by inserting the known 2 into formula. H = 50.6 DH = -.174 H = 41.7 DH = 2.98 V = 46.3 DV = .0 ABI Workshop on Emittance Measurements

19. MI8 Emittance Data Logging Booster moved extraction position at MP02 vertically by 1.5 mm. v H Unpredictable change of the lattice parameters (Dispersion) due to skew components in the extraction elements  ABI Workshop on Emittance Measurements

20. Beam Sigma NuMI Beam-line with Q101 Error Q101 error included in calculation ABI Workshop on Emittance Measurements

21. Beam Sigma NuMI Beam-line after Correction ABI Workshop on Emittance Measurements

22. Optical Transition Radiation (OTR) • Transition radiation • Charged particles passes through a media boundary • Monitoring of trans. beam profile (-> emittance), bunch length and energy beam beam courtesy A. Lumpkin ABI Workshop on Emittance Measurements

23. OTR for Protons & pBars • Beam intensities of 2.4e13 and 4.1e13 • Gaussian fits to beam projections • Higher intensity beam has larger ellipticity and beam tilt • This show an advantage of a 2-D imaging device over 1-D profile monitors ABI Workshop on Emittance Measurements

24. OTR Kapton Foil Aging • Operate primary foil ~3 months of continuous beam • Total: ~6.5e19 protons • Insert secondary foil under similar beam conditions • Secondary foil generating ~25% more OTR • Aluminized Kapton is degrading ABI Workshop on Emittance Measurements

25. 1.7 GHz Schottky Detector ABI Workshop on Emittance Measurements

26. Calibration with Scrapers* * Actual calibration compensated for betatron coupling In X-X’ or Y-Y’space… X’ X Graphic representation of destructive emittance measurement with mechanical scraper (for calibration) ABI Workshop on Emittance Measurements

27. Vector Signal Analyzer Display • Measurements: • Momentum spread • Longitudinal emittance • Transverse emittances • Betatron tunes • Other potentials: • Chromaticities • Beam intensity • beam-gas scattering(asymmetry in energyspectra of DC beam) ABI Workshop on Emittance Measurements

28. Flying Wires after Instability Horizontal profiles before and after instability in the Recycler (emittance growth through coupling) Vertical profiles before and after instability in the Recycler ABI Workshop on Emittance Measurements

29. Upcoming Projects at Fermilab DUSEL beam-line MTA beam-line NOvA µ-to-e HINS NML Project X (8 GeV SCRF linac) ABI Workshop on Emittance Measurements

30. HEP Challenges ABI Workshop on Emittance Measurements

31. Project X • 2 MW proton beam @ 50-120 GeV for neutrino physics • 1.6e14 / 1.4 sec at 122 GeV: 2.1 MW • 20 mA, 1.25 msec, 5 Hz from H- linac • Strip in Recycler • Single turn transfer into MI • Kaon and Muon physics at 8 GeV, simultaneously • 3 pings from Recycler to Accumulator • 7e13 / 1.4 (0.7) sec at 8 GeV: 70 (140) MW for mu2e • 3 (6) x over NOvA era beam power • Investigate slow spill extraction • A path towards a neutrino factory, possible muon collider • Upgrade path to 10 Hz, longer pulse length November 21-22, 2008: Project Collaboration Meeting (http://projectx.fnal.gov) ABI Workshop on Emittance Measurements

32. Beam Parameters ABI Workshop on Emittance Measurements

33. Linac Layout ABI Workshop on Emittance Measurements

34. Site Plan ABI Workshop on Emittance Measurements

35. Challenges (Emittance Diagnostics) • Transport of high intense hadron beams requires • Non-invasive beam diagnostics! • Well calibrated monitoring of beam profiles for beam emittance monitoring • Monitoring/mitigation of beam halo and tails (transverse and longitudinal) • Transverse beam size / emittance • Physical (intercepting) wires(?), e.g. scanners, slit / mulitwire, etc. • Laser wire, laser emittance (only H- beams) • Ionization profile monitors (calibration!) • e-beam scanner • Beam halo characterization (sensitivity, safety) • crawling wire • mode-locked laser wire • vibrating wire • Longitudinal diagnostics • microwave Faraday-cup • bunch shape monitor (wire-based) • Allison scanner (at low energies) ABI Workshop on Emittance Measurements

36. BNL Laser Wire for HINS • BNL test: • 750 keV H- beam • Faraday-cup e- detector ABI Workshop on Emittance Measurements

37. Fermilab LPM Test Setup • Laser Profile Monitor details • Q-switch laser • Laser energy: 50 mJoule • Wavelength: 1064 nm • Pulse length: 9 nsec • Fast rotating mirrors(±40 / 100 µsec) • e- detector: scintillator & PMT • Installation: • 1st Test with 400 MeV H- • HINS: 2.5 & 60 MeV • Upgrades & issues • CW laser for single macro pulse sweep • Detector system for 8 GeV setup detector port BPM BPM H- beam double dipole laser beam optical box ABI Workshop on Emittance Measurements

38. Summary • Fermilab successfully operates a variety of beam monitors, helping to evaluate the beams transverse / longitudinal emittance. • While the beam measurement based part, i.e. profiles, momentum spread, etc. report reliable data, uncertainties in the lattice parameters limit the overall precision (error) of the emittance measurement to ~15-20 %. • Measurements in high dispersive areas tend to much larger errors. • Fermilabs future intensity frontier Project X, based on SCRF accelerating structures, needs sensitive, non-invasive beam profile detectors. ABI Workshop on Emittance Measurements

39. Backup ABI Workshop on Emittance Measurements

40. MuMI Beam Profile / Loss • The NuMI 120 GeV/c proton beam for neutrino production currently operates at beam power to 320 kW. Near term this will increase to 400 kW with dedicated Main Injector beam, and with upgrades, to 700 kW for supporting the NOvA experiment. Project X era beam will further increase this by ~ x 3 to > 2 MW. • NuMI operation requires maintaining fractional beam loss to less than ~ 10-5 of the operational intensity beam to provide environmental ground water protection. Normal fractional beam loss seen along the transport is a few x 10-7. • 10 thin foil (5 µm x 140 µm Ti strips at 0.5 – 1.0 mm pitch) profile monitors are currently installed along the NuMI transport line. • The pre-targeting monitor, which can be left in the beam has performed well with good signal longevity in the beam of 1.1 mm rms, integrating over 3 x 1020 protons on target. • To enable high intensity operational usage of the other beam transport monitors, an improved mechanical drive system has been successfully developed which provides precision monitor positioning into the beam during high intensity operation with no beam loss other than from the SEM strips. • Prototype efforts are also ongoing to reduce monitor material exposed to the beam, enabling multiple monitors to be inserted at high intensity. • Design constraints include minimizing beam interactions, stable signal response for prolonged beam exposure, robustness to beam heating effects and maintaining adequate mechanical robustness for the SEM grids while minimizing beam loss. ABI Workshop on Emittance Measurements

41. Operation Scenario ABI Workshop on Emittance Measurements