CESR Test Accelerator Optics Correction and Tuning Tools David Sagan Cornell University

March 6, 2007 ILCDR Frascati 2 Outline CesrTA Overview Betatron phase & coupling measurement & correction Alignment & vertical emittance Survey & alignment Instrumentation for ultra-low emittance measurement Conclusion

March 6, 2007 ILCDR Frascati 3 Unique Features of R&D at CESR The only operating wiggler-dominated storage ring in the world The CESR-c damping wigglers -Technology choice for the ILC DR baseline design Flexible operation with positrons and electrons Flexible bunch spacings suitable for damping ring tests -Can operate down to 4ns (or 2ns) spacings with suitable feedback system upgrades Flexible energy range from 1.5 to 5.5 GeV -CESR-c wigglers and vacuum chamber specified for GeV operation -An ILC DR prototype wiggler and vacuum chamber could be run at 5 GeV CESR offers:

March 6, 2007 ILCDR Frascati 4 CesrTA Goals Electron cloud measurements -e - cloud buildup in wigglers -e - cloud mitigation in wigglers -Instability thresholds -Validate the ILC DR wiggler and vacuum chamber design Ultra-low emittance operations and beam dynamics -Study emittance diluting effect of the e - cloud on the e + beam -Detailed comparisons between electrons and positrons -Also look at fast-ion instability issues for electrons -Study alignment issues and emittance tuning methods -Emittance measurement techniques ILC DR hardware development and testing -ILCDR wiggler prototype, wiggler vacuum chamber, 650 MHz SRF, kickers, alignment & survey techniques, instrumentation, etc. Primary Goals: The Cornell CESR Storage Ring is in a position to make significant contributions to these R&D issues.

March 6, 2007 ILCDR Frascati 5 2 GeV Design Lattice xx yy xx Wigglers ParameterValue E2.0 GeV N wiggler 12 B max 2.1 T xx 2.25 nm QxQx QyQy 9.63 QzQz  E /E 8.6 x  x,y 47 ms  z (with V RF =15MV) 6.8 mm cc 6.4 x  Touschek (N b =2x10 10 &  y =5pm ) 7 minutes

March 6, 2007 ILCDR Frascati 6 IBS Evaluation (2 GeV Lattice) Horizontal Emittance (nm) Vertical Emittance (pm) Assumes coupling dominated Bunch Length (mm) 10 3 x Energy Spread Growth by 3.5x

March 6, 2007 ILCDR Frascati 7 Alternate Operating Point Horizontal Emittance Vertical Emittance Bunch Length Growth by 1.6x Want to study ECE impact at ILC DR bunch currents GeV lattice with  z ~ 9mm - Zero current vertical emittance chosen to be consistent with above alignment simulations - This emittance regime appears consistent with studying the impact of the ECE (and other effects) on emittance dilution

March 6, 2007 ILCDR Frascati 8 Betatron Phase & Coupling Measurement Coupling and betatron phase and are measured by shaking the beam at a betatron resonance and looking at the response at the BPMs. -Sample the position at a BPM 16k times. -Shake simultaneously horizontally and vertically. -To filter signal look at average of: (x, y) * e i  r t -Measurement time 40 sec. for 100 BPMs. -Resolution ~ 0.1 o

March 6, 2007 ILCDR Frascati 9 Phase / Coupling Correction Correction involves minimizing a Merit function: M =  i W i (Data meas - Data design ) 2 +  j W j (Var meas - Var fit ) 2 Horizontal Betatron Phase Vertical Betatron Phase Cbar12 Coupling Parameter Detector # Vertical Betatron Phase Cbar12 Coupling Parameter Horizontal Betatron Phase Before: Measurement - Design After: Measurement - Design Detector #

March 6, 2007 ILCDR Frascati 10 Locating Errors The phase and coupling data can be used to locate and measure the strength of quadrupole and skew quadrupole errors. Example: A backleg winding for a steering coil accidentally located near the beam pipe caused a skew quadrupole filed in the vicinity of the beam. Location of coupler

March 6, 2007 ILCDR Frascati 11 New BPM Electronics BPM Readout Module Block Diagram With all BPMs instrumented with individual readout modules, coupling, betatron phase, and position measurements could be made in real time (~1 second). ~5k$ / BPM installed.

March 6, 2007 ILCDR Frascati 12 CesrTA: Alignment & Vertical Emittance Misalignment Nominal Value Quadrupole, Bend, and Wiggler Offsets 150  m Sextupole Offsets 300  m Quadrupole, Bend, Wiggler, and Sextupole Rotations 100  rad In CesrTA the vertical emittance is sensitive mainly to the vertical alignment. Nominal CesrTA alignment capabilities:

March 6, 2007 ILCDR Frascati 13 Vertical Emittance Correction CesrTA Simulation: Correcting the vertical dispersion and coupling using steerings, and skew quads, the vertical emittance can be corrected to a factor of ~3 of the ILC DR. Correcting the vertical dispersion with steerings gives the greatest benefit. BPM ErrorRMS Value Absolute 10  m Relative 2  m Rotation 500  rad 3.2 pm mean % After CorrectionBefore Correction

March 6, 2007 ILCDR Frascati 14 CesrTA: Survey and Alignment collider component Rapid Tunnel Reference Surveyor (RTRS) Concept Proposal submitted for ILC DR alignment and survey studies using CesrTA Tunnel Wall wall markers internal FSI external FSISM beam LiCAS technology for automated stake-out process A. Reichold

March 6, 2007 ILCDR Frascati 15 Instrumentation for Ultra-Low Emittance Measurement Typical Beam Sizes –Vertical:  y ~10-12  m –Horizontal:  x ~ 80  m (at a zero dispersion point) Have considered laserwire and X-ray profile monitors –Fast x-ray imaging system (Jim Alexander) Core diagnostic for CesrTA – high resolution and bunch-by-bunch capability Plan for integrating systems into CHESS lines First pinhole camera tests were successful! (see next slide) –Laserwire CESR-c fast luminosity monitor offers window suitable for laserwire use Detector potentially could be used for fast segmented readout of Compton photon distribution

March 6, 2007 ILCDR Frascati 16 GaAs Detector for X-ray Imaging Signal (ADC Counts) Position (  m) Fast enough for single bunch resolution  = 142 +/- 7  m Different symbols represent different bunches NEW: GaAs arrays from Hamamatsu 1x512 linear array 25  m pitch 1 st sample has just arrived First bunch-by-bunch beam size data  [Test setup used pinhole camera]

March 6, 2007 ILCDR Frascati 17 Luminosity Monitor Window Available for laserwire use Aluminum  Window –Faces into South IR –~1 in thick (0.26 X 0 ) –16.1 m from center of CesrTA insertion region –Looks at e + beam –Aperture (for 16.1 m): +/- 1.7 mrad vertical -7 to +2 mrad horizontal (negative is to inside of ring) A similar window, but with smaller horizontal aperture, could potentially be added for monitoring the electron beam

March 6, 2007 ILCDR Frascati 18 Conclusion The ability to rapidly correct the orbit, dispersion and lattice functions is essential for maintaining the required horizontal and vertical emittances. Individually powered magnets provides great flexibility. Software and hardware has been developed which permits the measurement of orbits, dispersion, betatron phase, and coupling data. Software has been developed which allows simultaneous correction of all data using any combination of steerings, quadrupoles, and skew quadrupoles. Software has been developed to detect steering, qudrupole, and skew quadrupole errors. Software has been developed to calibrate steerings, quadrupoles, and skew quadrupoles.

March 6, 2007 ILCDR Frascati 19 Conclusion Con't CesrTA conceptual design work is ongoing –The machine offers unique features for critical ILC damping ring R&D CESR-c wigglers Operation with positrons and electrons Flexible bunch configuration Wide range in operating energy –Simulations indicate that the emittance reach is suitable for a range of damping ring beam dynamics studies –The experimental schedule will allow timely results for ILC damping ring R&D