# Presentation: 158007

## Rf and x-ray optics issues in generating ultra short pulses at APS with deflecting cavities

*Katherine Harkay*
*Accelerator Physics Group*
*Accelerator Systems Division*
*Advanced Photon Source*
*Diamond Light Source,   September 16, 2005*

## Outline

- Science case
- Introduction to rf deflection
- Rf deflecting cavities
- RT vs SC
- Challenges
- X-ray optics
- R&D plan
- Summary

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Feasibility study group*

- Beam dynamics
-   M. Borland
-   Y.-C. Chae
-   L. Emery
-   W. Guo
-   K.-J. Kim
-   S. Milton
-   V. Sajaev
-   B. Yang
-   A. Zholents, LBNL

- RF
- K. Harkay
- D. Horan
- R. Kustom
- A. Nassiri
- G. Pile
- G. Waldschmidt
- M. White
- V. Dolgashev, SLAC

- Undulator radiation & x-ray optics
-   L. Assoufid
-   R. Dejus
-   D. Mills
-   S. Shastri

- * All affiliated with APS except where noted

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Science drivers for ps x-rays

**APS Strategic Planning Workshop (Aug 2004): Time Domain Science Using X-Ray Techniques**
*“...**by far, the most exciting* *element of the workshop was exploring the possibility of shorter timescales at the APS, i.e., the generation of 1 ps x-ray pulses whilst retaining high-flux. This important time domain from 1 ps to 100 ps will provide a unique bridge for hard x-ray science between capabilities at current storage rings and future x-ray FELs.”*

**APS User’s Meeting: Workshop on Generation and Use of Short X-ray Pulses at APS (May 2005)**

**Atomic and molecular dynamics, coherent/collective processes:**
- Atomic and molecular physics
- Condensed matter physics
- Biophysics/macromolecular crystallography
- Chemistry

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## 10-16

**10****-16**

**10****-14**

**10****-12**

**10****-10**

**10****-8**

**10****-6**

**10****-4**

**10****-2**

**10****0**

**10****2**

**10****4**

**10****6**

**Ultrasonic**

**NMR**

**WORKSHOP ON TIME DOMAIN SCIENCE USING X-RAY TECHNIQUES**

***Storage Ring Sources***

**EPR**

***X-ray FELs***

**Slide courtesy D. Reiss, U. Michigan**

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## X-ray FELs & storage ring ps sources are complementary

**Note: Femtoslicing not practical at APS (calc per A. Zholents)**

- Energy modulation E=7e requires:
** **~10 mJ laser pulse at L=400 nm and =50 fs** **
- giving ~ 100 fs x-ray pulse with ~ 105 photons per pulse
- BUT: looks difficult at a high rep. rate

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Crabbing scheme†

- Deflecting (“crab”) cavity operating in TM110 mode; phased such that Bx deflects head and tail of bunch in opposite directions vertically (chirp, not tilt)
- Electron (& photon) vertical momentum correlated with longitudinal position as bunch evolves through lattice
- Second crab cavity at nπ betatron phase cancels kick; rest of storage ring nominally unaffected

**† ****A. Zholents, P. Heimann, M. Zolotorev, J. Byrd, NIM A425 (1999)**

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Generation of ps-pulses

**For APS: h=8, 6 MV deflect. voltage, ****σ****y’,e**** = ****2.2 μrad, and ****σ****y’,rad**** = ****5 μrad; the calc’d compressed x-ray pulse length is ~0.36 ps rms.**** **

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Outline

- Science case
- Introduction to rf deflection
- Rf deflecting cavities
- RT vs SC
- Challenges
- X-ray optics
- R&D plan
- Summary

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Crabbing and parasitic modes (KEKB)†

***Crabbing and parasitic modes (KEKB)******†***

- TM110

- TM010

- TM110

- TE111

- 500MHz

- 500MHz

- 324MHz

- 720MHz

- Unwanted modes

- TM110 - like Mode

- 500MHz

- TM010 - like Mode

- 413.3MHz

- 700MHz

- 650.5 MHz / 677.6MHz

- Unwanted modes

- Crab Mode

- Crab Mode (h):
- B, Ez off axis

- E

- B

**The squashed cell shape cavity scheme was studied extensively at Cornell in 1991 and 1992 for CESR-B under KEK-Cornell collaboration**.

- † Courtesy K. Hosoyama, KEK, APS ps workshop (2005)

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Parasitic modes (cont)

- Vertical crabbing mode (APS): horiz axis “squashed”
- Maximize mode separation for optimized damping
- HOMs above beam pipe cutoff, propogate out
- Lower-order mode (TM010) may strongly couple to beam; freq. below cutoff, adopt KEKB coaxial line strategy (for SC)
- Multiple cells produce multiplicity of parasitic modes (issue for SC)
- Orbit displacement causes beam loading in crabbing mode; adopt KEKB criterion of y = ±1 mm (for orbit distortions ± 0.1 mm)
- Generator power increased to compensate; de-Q to decrease sensitivity

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Instability thresholds from parasitic mode excitation(per Y-C. Chae)

***Instability thresholds from parasitic mode excitation******(per Y-C. Chae)***

- APS parameters assumed:  I = 100 mA, E = 7 GeV, =2.8e-4, s/2=2 kHz, s=0.0073, x = 20 m

- [1] A. Mosnier, Proc 1999 PAC.
- [2] L. Palumbo, V.G. Vaccaro, M. Zobov, LNF-94/041 (P) (1994; also CERN 95-06, 331 (1995).

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Parameters/constraints: what  hV  is required? 

***Parameters/constraints: what  hV****** ****** is required? ***

- Coutesy M. Borland, APS ps  Workshop,  May 2005

**Cavity design and rf source issues**
**h=7, V<6 MV?**

- V=4,  h=6

- V=6,  h=4

- V=6,  h=8

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Space constraints at APS

- Nominal 2-sector implementation shown: 4 IDs and 2 BMs
- Nominal insertion length available for rf cavities: 2.5 m

- 5 m

**Dipole Magnet**

**Undulator**

**Deflecting Cavity**

**= Multi-cell SC cavity or NC structure**

- M. Borland, Phys. Rev. ST Accel. Beam 8, (2005)

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Summary of rf design considerations

- Goal 1 ps in crab insertion
- No impact of crab cavities on performance outside insertion
- Beam dynamics simulation study (M. Borland)
- h ≥ 4 (1.4 GHz)
- Deflecting voltage  ≤ 6 MV (lifetime)
- Availability of 100-kW class rf amplifiers limits study to h = 8 (2.8 GHz)
- Available insertion length for cavities nominally 2.5 m (could be extended)
- Effects of errors: emittance growth or orbit kicks (M. Borland)
- Intercavity phase error < 0.04 for <y’>/σy’ < 10%
- Intercavity voltage difference < 0.5%
- Significant parasitic mode damping requirement (Y-C Chae)

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Deflecting cavity international effort (select)

- Deflecting cavities pursued for many applications by many research institutions.
- 1960’s – BNL investigated S-band RT cavity for beam separator; other labs also
- 1970’s - CERN investigated 2.86 GHz SC cavity for separating kaon beam
- 1991 - Cornell tested 1.5 GHz scale model
- 1993 to present – KEK prototyped 500 MHz cavity for crab crossing, colliding beams.  Installation planned in 2006.
- SLAC developed RT SW deflecting cavity as a LC damping ring fast kicker
- 2000 to present – FNAL prototyping 3.9 GHz CKM deflecting cavities (also now ILC).
- 2004 to present – APS investigating deflecting cavity design options for ps pulse generation.
- Present – CERN, ALS, others exploring crab cavity concepts, HOM-free, for ILC, etc

- G. Waldscchmidt, K. Harkay

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Room temperature (RT) vs. superconducting (SC) rf(K. Harkay, A. Nassiri)

- No installed “crab cavity” in existing synchrotron facilities
- KEKB plans to install two SC single cell cavity in March 2006
- RT pulsed system allows user to “turn off” ps pulse via timing (~1 s pulse, 0.1 – 1 kHz rep rate) (M. Borland, P. Anfinrud)
- SC system runs CW, rep rate up to bunch spacing; some experiments desire high rep rate (no pump probes) (D. Reiss)
- Either option requires dedicated R&D effort

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## RT vs. SC rf

- RF sources
- for SC option are available with minimal reconfiguration
- for RT are non-typical and modification is required (1 kHz)
- Cavity fill time vs. susceptibility to phase noise
- Long for SC cavity; makes it less susceptible
- Short for RT structure; makes it more susceptible
- Need to compensate frequency detuning
- Due to pulse heating for RT case
- From microphonics for SC case

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Suppression of parasitic modes 
Challenging for SC cavity, multiple cell cavities in particular
Well understood for RT structure
Need to study and understand transients during pulsing of RT structure and its effect on SR beam. How does it affect “non-crab” beamline users?
Cost: SC option approx 2x RT option
Overall, SC option is more attractive 
May offer a greater degree of compatibility with normal SR operation
Compatible with future development of higher rep rate pump probe lasers
Opportunity for APS to gain SC rf expertise

- Challenging for SC cavity, multiple cell cavities in particular
- Well understood for RT structure
- Need to study and understand transients during pulsing of RT structure and its effect on SR beam. How does it affect “non-crab” beamline users?
- Cost: SC option approx 2x RT option
- Overall, SC option is more attractive
- May offer a greater degree of compatibility with normal SR operation
- Compatible with future development of higher rep rate pump probe lasers
- Opportunity for APS to gain SC rf expertise

***RT vs. SC rf***

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## RT rf deflecting cavity study for APS

- RT rf slides courtesy:
- V. Dolgashev, SLAC, APS Beams and Applications seminar, June 2005
- and
- A. Nassiri

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Design consideration

- Limited available power ≤ 5 MW
- Large aperture ~2 cm => Low impedance
- Maximum surface electric fields < 100 MV/m
- Pulsed heating < 100 deg. C  => maximum surface magnetic field        < 200 kA/m for 5 μs pulse
- Deflecting mode degeneracy fixed by wall deformation during tuning
- “Smooth” coupler – no field amplification on edges

- 10 MW option

- V. Dolgashev, SLAC, APS seminar, June 2005

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Structure types: standing wave vs. traveling wave 

| Efficiency/length
Deflection vs. power | High | Low |
| --- | --- | --- |
| Filling time | Proportional to the quality factor
      Generally slow | Proportional to the group velocity and structure length 
          Generally fast |
| Deflecting field vs. number of cells n | Scales as  | Scales as 

                = attenuation |
| Maximum number of cell | Limited to about 10 because of mode overlapping | In principle there are no limitations |
| Circulator | Generally needed to protect klystron | Not necessary |
| Temperature sensitivity  | Need automatic tuning system or a very good temperature stabilization to maintain the cavity on resonance  | Less temperature sensitivity |

**                                                                                   ****SW                                                   TW****	**

- Courtesy A. Nassiri

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## 9 Cells SW Deflecting Structure

- V. Dolgashev, SLAC, APS seminar, June 2005

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Configuration

- Two 5 MW pulsed klystrons
- One modulator
-  Two 18-cell 1- meter structures

- Courtesy A. Nassiri

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Modulator 

- 5 MW Klystron
- 5 sec pulse length (MAX)
- 1 kHz rep rate
- Average power  25 kW
- Beam Voltage 150 kV
- Beam current 85 A
- 60 KV DC power supply
- Pulse rise time (10%-90%) <1sec
- Pulse fall time (10%-90%) <1sec
- Pulse voltage variation  ±0.1%

- Courtesy A. Nassiri

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Pulsed RF source

- Between 5 to 10 MW pulsed at 2815 MHz ( 8351.93 MHz)
- Requires 1 kHz pulse repetition rate
- Pulse length ~ 5 s
- No “off the shelf” klystron to buy
-  Closest:
-                   **CPI    VKS-8262F      2.856 GHz**
**                               ****5 MW Peak**
**                             ****16.3 ********sec pulse length **
**                             ****400 Hz rep rate              P****ave****=32 kW**
- Modified CPI klystron
-                   **2.815 GHz**
**                      ****5 MW Peak**
**                      ****5 ********sec pulse length   **
**                     ****1 kHz rep rate                             P****ave****=25 kW**
**                                          **

- Courtesy A. Nassiri

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## SC rf cavity study for APS (G. Waldschmidt, G. Pile, D. Horan, R. Kustom, A. Nassiri, K. Harkay)

- Assuming CW operation, power and space reqt’s favor SC:
-   RF losses
-   RT, single cell cavity: on the order of 10 MW
-   SC cavity: on the order of 25 W (2 K)
-   Single-cell vs. multiple-cell SC cavity configurations compared

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Squashed rf crab cavity (based on KEK design)

|  | 1-cell | 4-cell ( mode) |  |
| --- | --- | --- | --- |
| Frequency | 2.81 | 2.81 | GHz |
| No. of cavities | 7 | 3 |  |
| Phase advance | ---- | 180 | Deg |
| Cavity radius | 7.8 | 7.8  | cm |
| Iris radius | --- | 1.8 | cm |
| Beam pipe radius | 2.1 / 1.8 | 2.1 / 1.8 | cm |
| Deflecting voltage | 4 | 4  | MV |
| Deflecting gradient | 10.7 | 6.25 | MV/m |
| Qo | 3 x 109 | 3 x 109 |  |
| RT/Q | 52 * 7 | 220 * 3 |  |
| Active cavity length  | 5.3 * 7 | 21.3 * 3 | cm |
| BMAX | 95 | 80 | mT |
| Pbeam, 1mm offset | ~25 | ~25 | kW |
| RF loss at 2 K  | 15 | 10 | W |

**G. Waldschmidt,  APS ps Workshop, May 2005**

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## RF coupling and mode damping

**APT @LANL**

- Courtesy A. Nassiri

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## KEK B-factory

***RF coupling and mode damping***

- Courtesy KEK

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Two-Cell Deflecting Cavity

***Two-Cell Deflecting Cavity***

| Frequency | 2.81 GHz |
| --- | --- |
| VT | 4 MV |
| RT/Q | /m |
| Q | 1.0 x 109 |
| PL | 159 W |
| BMAX | 712 mT |

- Two-cell cavity
- Requires less space than single-cell
- Fewer parasitic modes than many-cell cavity
- Less opportunity for trapped mode
- Coaxial input coupler supplies power for 4 MV deflecting voltage at 2.81 GHz.
- Various damping scenarios investigated.
- Note: Maximum B-field will be easily reduced by enlarging center iris
- Estimate no more than (5) 2-cell cavities required.

- Courtesy Waldschmidt, Nassiri

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Coaxial Damper

- Beam pipe enlarged from 19 mm to 32 mm radius.
- 19 mm aperture for beam.
- 8 mm thick beam pipe damper for Nb and cooling channel
- 5 mm gap between inner and outer conductors
- Substantial deQing of LOM ~104
- Deflecting mode rejection filter not yet implemented
- Removal of LOM from beam pipe damper will likely be done using coaxial transmission line

- Waldschmidt

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Recent efforts re. damping parasitic modes (APS, 2-cell)

- Slide courtesy G. Waldschmidt

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Issues to be resolved

- Effective damping of HOM and LOM
-       - coaxial line in beam pipe
-       - radial line
-       - loop
- Deflecting mode input power coupling
-        - coupler design
-        - variable coupling
- Cavity optimization
-       - deflecting gradient in available insertion length
-       - shunt impedance
- Frequency
-      - rf source availability
-      - input power
-      - fill-time

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Issues to be resolved

- Extraction of LOM w/o disturbing deflecting mode excessively
- Accessing and eliminating the 0-mode in the TM11 passband - challenging task
- Proper deQing of all HOM’s
- Extraction of power from parasitic modes from coax beam pipe
- Remove heat load outside of cryo-module.
- Prevent heat loads too large for damping material
- Convert to waveguide input coupler for ease of cooling and construction – although possible added complexity for cryo system.
- Damping unwanted polarization of TM110 mode
- Impedance threshold for stability in the APS dictates strong damping of these modes
- HOM field profiles somewhat similar to the deflecting mode
- Frequency separation of the nearest HOM is ~9 MHz. Damping this mode may cause significant deQing of the deflecting mode
- Allowable deQing factor for the deflecting mode

- Courtesy A. Nassiri

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Advantages of KEK mode damper design

- Coaxial beam pipe on one side
- There is no cut-off frequency for TEM mode.  All monopole modes in the cavity can couple to the coaxial beam pipe as a TEM mode and propagate
- In addition, all dipole modes can couple to the coaxial beam pipe as a dipole mode wave and propagate
- Designing cavity cell shape such that fTE111 > fcutoff > fTM110
- One dipole parasitic mode still left trapped in the cavity (unwanted polarity crab mode)

- Courtesy A. Nassiri

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## CW RF Source (s)

- At what power?
-        - ~100 kW   (for 300 mA operation)
-        - ~40 kW  (for 100 mA operation)
- What frequency?
-        - 2.8 GHz ( 8th harmonic of the SR rf frequency)
-        - 1.4 GHz ( 4th harmonic of the SR rf frequency)

| Manufacturer | Tube | Frequency (GHz) | Output Power (kW) | Voltage (kV) | Current (A) |
| --- | --- | --- | --- | --- | --- |
| THALES | TH2110 | 2.856 | 50 | 26.5 | 3.3 |
| CPI | VKS-7975A | 2.45 | 120 | 34 | 6.3 |
| TOSHIBA | E3724 | 2.45 (h=7) | 100 | 42 | 4 |
| TOSHIBA | E3778 | 1.76 (h=5) | 1400 | 85 | 30 |
| TOSHIBA | E3750 | 1.4 | 25 | 19 | 2.5 |

- Courtesy A. Nassiri

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Outline

- Science case
- Introduction to rf deflection
- Rf deflecting cavities
- RT vs SC
- Challenges
- X-ray optics
- R&D plan
- Summary

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## X-ray compression optics design constraints

- Suite of beamlines to be determined
- Some compressed, others not
- Optimized for tuning range(s)
- Upgrades to existing ID beamline(s) include optics, modification of vertical apertures, etc
- Not trivial, but likely in line with typical new beamline commissioning timeframe of a few years
- Optimization:
- Compression throughput
- Pulse duration and spot size
- Energy tunability (5-30 eV)
- Issues: geometric effect, mirror

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## S. Shastri, APS ps Workshop, May 2005

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## X-ray compression optics (S. Shastri, R. Dejus, L. Assoufid)

***X-ray compression optics ****(S. Shastri, R. Dejus, L. Assoufid)*

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## X-ray compression optics simulation(R. Dejus)

***X-ray compression optics simulation****(R. Dejus)*

- 2D scatter plot, undulator A irradiance  at 30 m, 10 keV. Red = 10% level, green = 37% (1/e).; ~ 20% are thrown away. The tilt angle *β*  is ~ 55°.

- Pulse histogram using optics compression and a slit of 8.0 mm (half-width). The rms width is 1.19 ps (FWHM ~ 2.8 ps), and the transmission is 62%.

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Outline

- Science case
- Introduction to rf deflection
- Rf deflecting cavities
- RT vs SC
- Challenges
- X-ray optics
- R&D plan
- Summary

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## R&D Draft Plan

- Green light: begin construction, order long-leads, fabrication, etc
- Deliver operational system in ≤ 3 yrs

- Feasibility study completed
- SC rf technology chosen

- Model impedance effects (parasitic modes, head-tail)
- Finalize RF system design, refine simulations
- Refine x-ray compression optics design, end-to-end ray tracing
- Conduct proof of principle tests (beam dynamics, x-ray optics)
- Chirp beam using synchrobetatron coupling (transient) (W. Guo)
- Install 1 MV RT S-band structure, quarter betatron tune (M. Borland,  W. Guo)
- Install warm model of SC rf cavity (passive), parasitic mode damping       (K. Harkay)

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Ultrashort x-ray pulse generation test 1

- Transient, short pulses are generated using an alternate scheme based on synchrobetatron coupling (suitable for study, but not operation). At left, an image of the beam 0.3 ms after a vertical kick, using APS sector 35 optical streak camera. At right, a short pulse is observed using a 40 μm vertical slit (fit gives 5.8 ps rms, nominal bunch length 30 ps).

- W. Guo, K. Harkay, B. Yang, M. Borland, V. Sajaev, Proc. 2005 PAC** **

- Carry out a demonstration short-pulse x-ray experiment on APS beamline** **
- Structural molecular reorganization following photoinduced isomerization/ dissociation can be studied on a finer timescale. Transient pulse requires acquisition of entire x-ray absorption spectrum in a single shot. (L. Young and colleagues)

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Summary

- We believe x-ray pulse lengths ≤ 1 ps achievable at APS
- SC RF chosen as baseline after study of technology options
- Main rf challenges include parasitic mode damping and cavity optimization
- X-ray compression optics configurations studied
- Slits only: 1013 ph/s avg (~1% of normal flux)
- Compression: throughput 2-15x better than slits alone over energy range 30-5 eV, respectively
- Main optics challenges include very long focusing mirror if required
- Proof of principle R&D is underway: beam/photon dynamics, RT and SC rf
- Operational system possibly ≤ 3 yrs from project start

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005

## Select references

- Deflecting cavity method
- A. Zholents, P. Heimann, M. Zolotorev, J. Byrd, NIM A 425, 385 (1999).
- APS papers
- K. Harkay et al., “Generation of Short X-Ray Pulses Using Crab Cavities at the Advanced Photon Source, ” Proc. 2005 PAC.
- M. Borland, Phys. Rev. ST Accel. Beams, 074001 (2005).
- M. Borland, V. Sajaev, “Simulations of X-ray Slicing and Compression Using Crab Cavities in the Advanced Photon Source,” Proc. 2005 PAC.
- W. Guo et al., “Generating ps x-ray pulses with beam manipulation in synchrotron light sources, “ Proc. 2005 PAC.
- Recent APS workshops (talks)
- Future Scientific Directions for APS (http://www.aps.anl.gov/Future/Strategic_ Planning_Meeting/home.htm)
- 2005 APS Users Meeting: Workshop on Generation and Use of Short X-ray Pulses at APS (http://www.aps.anl.gov/Users/Meeting/)

- K. Harkay          RF and X-ray optics for generating ultra short pulses at APS         9/16/2005