# Presentation: 787181

## Advanced Accelerator R&D: Flat Beam Transform & Emittance Exchange

*Kwang-Je Kim                  **ANL & U of C*
*June 27, 2008  *
*ANL-UChicago-FNAL Collaboration  Meeting at Fermilab  *

## Emittance Exchange and Flat Beam Transform

-  **Emittance Exchange (EEX)**: Complete exchange between x- and z-phase spaces:  (x,z) (z,x)

* ***Flat Beam Transform (FBT)**: Transform a round photo-cathode beam to a flat beam with a desired *emittance* ratio in (x,y) phase space

* ****Applications often require a combination of  these manipulations***

## Flat Beam Transform

- Produce angular-momentum dominated beam and remove correlation
- R. Brinkmann, Y. Derbenev, and K. Floettmann (1999, 2001)
- Experimentally demonstrated at A0
- D. Edwards, et. al., emittance ratio of 40 at Fermilab A0 (Linac2000, PAC2001)
- Yin-e Sun, U of C thesis (2005)
- Ph. Piot, Y.-e. Sun, and KJK, emittance ratio>100 (PRSTAB 9, 031001, 2006)

## Emittance Exchange Scheme

- First dogleg provides dispersion at deflecting cavity.
- The cavity reduces the momentum spread of the beam and gives a shear deflection to the beam.
- The second dogleg finishes the exchange.
- The scheme improves on the previous approximate scheme by Cornacchia and Emma in which the second dog-leg is reversed.

- Diagram by Tim Koeth.

## Improve HG X-Ray FEL Performance(P. Emma, Z. Huang, P. Piot, KJK)

- Electron bunch emittance of current X-ray FEL projects is (xymwith Q=1 nC
- This is about 10 times larger than ideal (to match the x-ray beam phase space)
- Due to small energy spread, can make zm
- FBT: (xy, zm
- Exchange x & z  (xy, zm

- Q=30 pC, z=10 fs

-  Higher gain
-  Lower K
-  Lower E-energy

## To Obviate Electron Damping Ring from ILC

- Emittances of ILC electron bunches  are (xyzm
- These bunches are produced by a 5 GeV, 6 km damping ring
- Theemittance Txy)1/2 is too small for photocathode
- A possibility: (1, 1, 8)(50,0.02, 8)(8, 0.02,50)  (Ph. Piot)

## EEX Demonstration Experiment

**FNAL/A0**
- Initiated by Helen Edwards, December, 2006, and T. Koeth engaged
- (x, y, z): ()(120, 6, 6)m, Q=1 nC
- Use CKM cavity design and existing RF power
- Exciting dataTim will be able to graduate!
**ANL/AWA-NIU-TsingHua U**
- Argone Acclerator Institute activity, funded by LDRD
- (x, y, z): ()(3,3,10)m , Q=0.1 nC
- NIU (Marwan Rihauoi, GS) and Tsinghua U (defl. cavity)
- To be finished by 2010-2011
**ANL-FNAL collaboration**
- Bi-(Tri-) weekly meetings and common web page
- Especially productive in exchanging ideas on diagnostics

## A0 People

**Helen Edwards – *****The Boss***
- Don Edwards
**Ray Fliller *****(The  Manager) ***
**Yin-e Sun *****(Recently from ANL)***
**Jinhao Ruan – Laser, All things optical**
**Jamie Santucci – Operations**
***Tim Koeth – Rutgers Ph.D. Student***
**Artur Paytan – Yerevan U. Ph.D. Student**
**Mike Davidsaver – UIUC staff, controls**
**Grigory Kazakevich – Guest Scientist, OTRI**
**Manfred Wendt – Instrumentation, BPMs**
**Randy Thurman-Keup – Instrumentation, Interferometer**
**Vic Scarpine – Instrumentation, OTR and cameras**
**Alex Lumpkin – Instrumentation, Radiation Diagnostics *****(On leave from ANL)***
**Ron Rechenmacher – CD, controls**
**Lucciano Piccoli – CD, controls**
**Gustavo Cancelo – CD, Low Level RF**
**Wade Muranyi – Mechanical Support, Lead Tech.**
**Many Others from AD/RF, AD/MS**

## EEX at FNAL-A0

- An 80 kW klystron is available.

- A0 Photoinjector Layout with EEX beamline

***EEX at FNAL-A0***

- Dipoles

- Vertical
- Spectrometer

- 3.9 GHz TM110 (deflecting mode) Cavity

## First Deflected Beam by a CKM type Cavity

***First Deflected Beam by a CKM type Cavity***

- Operating phase
- for exchange

## Recent Measurements at A0( Tim Koeth)

- TM110 cavity strength, ko

- Vary cavity strength

- record vertical BPM reading

- Intro p from 9-Cell

- OFF

- 73%

- 90%

- 100%

- 105%

- Vertical Beam Position after
- Vertical Spectrometer (mm)

- As the cavity strength is increased, the momentum change after the exchange line is reduced

- Change the input momentum (0.70% Increments)
- Measure the vertical offset after exchange line spectrometer
- Increase Deflecting Cavity Strength

## Diagnostics for A0 EEX

**Prior to the exchange :**
- OTR screens for beam spot size measurement
- Slits for uncorrelated beam divergence measurement
*Combined with above gives a transverse emittance measurement*
- Horizontally bending spectrometer for energy and energy spread measurement
- Streak Camera for bunch length
**After the exchange:**
- Same diagnostics for measuring transverse emittance
- Vertically bending spectrometer for momentum spread
*Allows us to decouple the momentum spread measurement from any residual horizontal dispersion from the doglegs*
- Martin-Puplett interferometer for bunch length measurement
*Also the streak camera (> 1 ps)*

## Recent Measurements at A0 ( cont’d)

- A preliminary measurements of several of EEX matrix elements:

- Onto an attempt to directly measure the exchange:

|  | x [mm.mrad] | z [mm.mrad] |
| --- | --- | --- |
| INPUT | 6 | 120 |
| OUT (TM110 OFF) | -- | 188 |
| OUT (TM110 ON) | -- | 50.5 |

- Output energy spread measurement

- Bunch length measurement with a streak camera.
- (A. Lumpkin)

- TM110 Cavity OFF

- TM110 Cavity ON

- Resulting emittances values:

**Close to CSR increased emittace (R. Fliller)**

## ANL-NIU-TsingHua Collaboration For EEX

**AWA**
- Wei Gai (Leader)
- Sergey Antipov
- Manoel Conde
- Felipe Franchini (Tech)
- Feng Gao (Student)
- Chunguang Jing ( Euclid supported)
- Richard Konecny (Super Tech)
- Wanming Liu
- John Power
- Zikri Yusof
**APS**
- Kathy Harkay, (Yin-e Sun), (Alex Lumpkin)
**NIU**
- Philippe Piot
- Marwan Rihaoui (GS)
**TsingHua**
- Cavity fabrication

## Emittance Exchange (EEX) at the Argonne Wakefield Accelerator

***Emittance Exchange (EEX) at the Argonne Wakefield Accelerator***

- Gun

- Linac

- ICT1

- GV

- GV

- TQ1,TQ2,TQ3

- YAG1

- YAG2

- Emittance Exchanger

- x=10 m
- y=3 m
- z= 3 m

- x= 3 m
- y=3 m
- z= 10 m

- TM110

- Photoinjector

**AWA photoinjector:**
- Q=100pC;  K= 12 MeV;
- Laser: x=y=2.5 mm; z=1.15 ps;

**EEX beamline:**
- =15 deg;  x = 25 cm; k=4

**Overall Goal: exchange small ********z**** for large********x ****with**** ****small Q**** ****bunches**

- N.B.  Exchanged many idea with Fermilab Emittance Exchange Group

## Diagnostics for AWA EEX

**ANL diagnostics will be more challenging than A0 due to small longitudinal emittance, thus short bunch length**
**Spot size**
- OTR screens for beam spot size measurement (same as A0)
**Beam divergence**
- pepper pot, (allows us to look at correlations, including x-y for flat beam)
**Energy and energy spread before and after EEX: **
- Spectrometer (same as A0)
**Bunch length**
-  zero-crossing method with linac, deflecting cavity (short bunch)
- Exploring EOS ( help from Jinhao Ruan)
**In addition:**
- Time-of-flight monitor: stripline-based phase detection
- Longitudinal phase space: linac phase scan or deflecting cavity + spectrometer

## Deflector Cavity

- Cavity fabricated at
- Tsinghua U in Beijing

- Trajectory offset in a deflector cavity
- D. Edwards (theory), J. Power (simulation)
- Developed a theory to eliminate by adjust cavity parameters

***Deflector Cavity***

**Deflector cavity arrives from Tsinghua U (soon)**
**Installation to AWA beamline (Fall, 2008)**
**Improved Longitudinal Emit Measurement  with deflector cavity + Spectrometer**

## Slide 18