1. Marc Ross T9 – Snowmass 2001 Closing Plenary T9 – Diagnostics M. Ross/R. Pasquinelli Thursday, July 19 RD: 1) determine mixing between z and x/y 2) determine phase space halo parameters 3) develop effective collimation to localize activation relied upon for SNS ring Charge: Note promising RD; assess involved effort Selected 5 fundamental issues facing a variety of projects Issue 1:emittance propagation in linacs p & e Proton Drivers + VLHC (pseudo-linac): Problem: understand diffusion mechanisms Diffusion limits high power performance  activation caused by beam loss SNS beam loss limits < 1W/m (10 -6 ) SCRF cleanliness  severe limit on materials; systems SNS will use laserwire

2. Emittance propagation in linacs Linear Collider Problem: Control wakes, dispersion (  ) and coupling Single bunch wakes and  increase projected emittance  usually unrecoverable Filamentation follows in chromatic systems Practical approach: 1)BPM based emittance optimization 2)Measurement of projected emittance 3)Development of more direct diagnostics 1)BPM based (SLC-like): a)beam-based alignment  quad dither/shunt b)dispersion-free steering  correction of  E generated distortions c)global correction  empirical orthogonalization minimalization Integrated calibration, correction, analysis and error handling RD: How well does this really work? Tests: SLAC Linac, TTF Head-on image of ‘tilted’ beam  20 nm achieved in FFTB - Cband

3. Emittance propagation in linacs (2) Linear Collider 2) Transverse beam profile monitor LASERWIRE  the LC replacement of wire scanner Vital projected emittance predictor of luminosity Wire/Laserwire monitors measure only projection  don’t directly provide source location RD: Develop accurate monitor for projected emittance High beam power; small spot sizes (resolution); large aspect ratio Tests: ATF, TTF, CTF “Ability to make measurements at the diagnostic and predictive level as opposed to measurement of the end result” KEK – ATF ring laserwire

4. Emittance propagation in linacs (3) Linear Collider 3) Direct measurement of beam ‘tilt’ Use cavity BPM dipole mode ‘crab’ structure in reverse for high disruption, y – z correlation serious concern RD: Develop monitor for beam y(x)– z correlation Test in FFTB, ATF ( Develop monitor for ‘slice’ emittance FEL RD) a pair of macro particles:   tt q/ 2   EXAMPLE: Bunch length:  t = 200  m/c = 0.67 ps Tilt toleranced = 200 nm Cavity FrequencyF = 11.424 GHz Ratio of tilt to position sensitivity: ½  f  t = 0.012 A bunch tilt of 200 nm / 200  m yields as much signal as a beam offset of 0.012 * 200 nm = 2.4nm Need BPM resolution of ~ 2 nm to measure this tilt

5. Issue 2:Bunch length & longitudinal dynamics - linacs   z Linear Collider LC/FEL linacs use multiple compression stages result is highly distorted z phase space TESLA, N/JLC  z ~ 100  m RD: Resurrect deflection structure and test SLAC FEL - LCLS Compression stages in FEL linac Transverse deflecting structure -- ‘crab’ Rotate (pitch/yaw) in order to display z on screen: 500 GeV streak camera

6. Issue 3:Single bunch instabilities e+e- ring factories & LC & proton rings Emittance degradation from ambient particles – ions/electrons e- cloud generated by SR/photo-electric effect; multiplied by secondary emission (e+ only; e- disperses cloud) Can cause 4x variation in L bunch/bunch Resonant behavior – bunch spacing; charge; vacuum chamber dimensions; local fields RD: Validate simulations by measuring cloud properties (joint beam dynamics/diagnostics effort) Develop b/b L phenomenology B-Factory operation/MD PEP-2 example fill pattern: Large ion gap small trains alternating between 9 and 10 bunches long train head intensity ramp 4 bucket spacing (design 2) 657 bunches filled out of ~ 1500 planned in design Electron cloud analyzer - APS

7. Issue 4: Integration Example: SC proton collider rings TeV/HERA/LHC Chronic operational limitation Remember GAN? RD: Develop instantaneous chromaticity monitor for feedback (CERN/DESY test) Other optical stabilization? Use head/tail (  E) oscillation difference: “If it is difficult to accomplish locally – a very different approach is required for remote operation”

8. Issue 5: Accelerator RD Example:  -cooling m uses SC magnets and high gradient RF (Combination of e/p!) Measure profile inside cooling channel using: Thermal network on hydrogen vessel Scintillating fibers Very little space for diagnostics! RD in parallel between machine and its tools Critical evaluation of emittance reduction experiment needed

9. Marc Ross T9 – Snowmass 2001 Closing Plenary Beam Diagnostics: T9 participation representative of Snowmass diversity (~15)  Cross flow of information unique to Snowmass Active discussion RD interest from a wide variety of groups T9 – Diagnostics M. Ross/R. Pasquinelli