Concluding Remarks

1) Take stock of the situation of the different machines, schemes, studies and R&D’s.

2) Gather information on the new technologies (fiber laser, mirrors…). Define the possible associated R&D’s.

3) Find the overlap with the undulator solution, both for funding (EU FP7…) and common work.

4) Benchmark of the GEANT4 polarized version. 5) Review the industrial – medical applications of Compton machine (extremely

important for R&D fund request).

CLIC - Redefine the parameters. Analyze the differences from the earlier proposal and

have a first “feasibility” scheme.ILC- Converge towards a scheme that can produce a valid “alternative” design and

clearly assess what R&D’s are necessary to validate the scheme.- Point the way to EDR- Study the possibility of a demonstrator experiment- Define the aspects of the schemes that still need answering (stacking,

costing…) and make a work planSuperB - Introduce the new machine and address the case of polarized positrons.

Introduce the FP7 design study

Workshop Goals

1st: Physics (users)• Physics = f( L,P,E) => Flexible machine= flexible

(POLARISED) positron source. • Is there a ~ factor 3 rule?• f = ? In te different cases….

Layout of positron damping ring system showing the parallel spin rotation beam lines for randomly selecting positron polarization direction. A pair of kicker magnets is turned on between pulse-trains to deflect the beam to the spin rotation solenoids with negative B-field.

space for spin rotators must be foreseen

K. Moffeit et al.,SLAC-TN-05-045

Take stock of the proposed solutions & technology

• Projects : ILC, CLIC ….SuperB

1 CLIC => New parameters : three schemes proposed

Major CLIC parameters changes

In January 2007, new CLIC key parameters have been adopted:

Accelerating gradient:

150 MV/m => 100 MV/m

RF frequency:

30 GHz => 12 GHz

=> All CLIC study is today under revision, in particular the CLIC Injector complex and the e+ production (polarized and unpolarized).

NLC

(1 TeV)

CLIC 2007

(3 TeV)

ILC

(Nominal)

Energy E GeV 8 9 15

Bunch population N 109 7.5 4 - 4.1 20

Nb bunches / train nb - 190 311 2625

Bunch spacing tb ns 1.4 0.667

(8 RF periods)

369

Train length tpulse ns 266 207 968625

Emittances x , y nm, nm.rad 3300, 30 600, 10 8400, 24

rms bunch length z m 90-140 43 - 45 300

rms energy spreadE 0.68

(3.2 % FW)

1.5 - 2 1.5

Repetition frequency frep Hz 120 50 5

Beam power P kW 219 91 630

Main beam parameters comparison

At the entrance of the Main Linac for e- and e+

The CLIC Injector complex (Compton)

3 TeV

Laser Compton configuration

Laser

Laser

DC gunPolarized e-

Pre-injector Linac for e-

200 MeV

e+ Target

Pre-injector Linac for e+

200 MeV

Inje

ctor

Lin

ac

2.2

GeV

e+ DR2.424 GeV360 m

Boo

ster

Lin

ac

6.6

GeV 3 GHz

e+ BC1 e- BC1

e+ BC2 e- BC2e+ Main Linac e- Main Linac

12 GHz, 100 MV/m, 21 km 12 GHz, 100 MV/m, 21 km

1.5 GHz

e- DR

e- PDR

1.5 GHz 1.5 GHz

3 GHz162 MV

3 GHz162 MV

12 GHz2.3 GV

12 GHz2.3 GV

9 GeV48 km

30 m 30 m

10 m 10 m

360 m

150 m

15 m 15 m

2.424 GeV360 m

2.424 GeV 2.424 GeV

e- Drive Linac 1.3 GeV

Compton ring

e+ PDR and Accumulator

ring

3 GHz

RF

gun

Stacking cavity

• 2 ILC baseline and alternative

The asymmetriespreliminary

preliminary

Undulator

Compton Ring

POSIPOL07. Compton Ring Lattice.

E = 1.070 GeV E = 1.300 GeV

Parameter With chic. Without chic. With chic. Without chic.

Gamma’s energy, MeV 10 – 20 10 – 20 15 – 30 15 – 30

Circumference, m 800 1280 1200 1920

Energy acceptance, % 7 5.5 7 5.5

Laser flash energy, J 2 2 2 2

Laser waist (RMS), μ 15 15 15 15

Laser pulse length (RMS), mm 0.5 0.5 0.5 0.5

RF voltage, MV 2×40 20 2×50 30

Bunch length, mm 4 – 6 4 – 6 4 – 6 4 – 6

Bunch charge, nC 2 2 2 2

Bunch spacing, cm 48 48 48 48

Stored current, A 1.25 1.25 1.25 1.25

Energy losses (SR + wigglers), keV

700 700 1000 1000

Particles losses per sec., % < 20 < 20 < 20 < 20

Positron number per sec. 1.051014 1.051014 1.051014 1.051014

MARS (Multiturn Accelerator-Recuperator Source)MARS (Multiturn Accelerator-Recuperator Source)

8 GeV

2.6 GeV

E = 1.8 GeV

~1Å

~12Å

InjectorBeam dump

G. N. Kulipanov, A. N. Skrinsky and N. A. Vinokurov, 1997

ERL

ERL bunch charge

Laser & optical cavity e+ stacking

Selection of bunch repetition: frep

3 factors to determine frep

163 MHzpreferable

40.8 MHzpreferable

40.8 MHzpreferable

Conclusions:•15% of the x-ray energy goes into harmonics•The x-ray signal filtered by the 10-m Ag foil consists primarily of harmonics•0.2 nC bunch contains 1.25109 electrons, i.e. 4 times the number of photons generated at IP. However, due to the approximately two times bigger cross-section of the e-beam compared with the laser focus, only ~¼ of the total electrons in the bunch participated in scattering.• Thus, we conclude that x-ray yield is close to N/Ne~1, as is required for ILC.

Quantitative agreement of the BNL experiment results

e-beam - size 60 m (RMS), charge 0.2 nC, duration 3.5 ps (FWHM); laser - energy 2 J, size 35 m (RMS), duration 5 ps (FWHM).

Parameter total harmonics

Number of x-ray photons at IP 3108 1.6107

Integral x-ray energy at IP (eV) 1012 1.51011

Number of x-ray photons at detector 7107 1.5107

Energy on detector (eV) 41011 41010

Filtered energy on detector (eV) 3.11010 3.01010

Agrees with experiment

LINAC

Polarized Electrons: Yes And what about positrons?

• Is a polarized positron source interesting for the SuperB factory?

• Yes!

SUPERB

2) Gather information on the new technologies (fiber laser, mirrors…). Define the possible

associated R&D’s.

• Technical aspects

• LASERS!!!!!!• CAVITIES (electronics, mechanics…)• Polarimetry• Mirrors• Too much to say only few snapshots

Laser Diode

PM - LMA fiber

OIPCF fiber

High power Laser Diode

Femtosecond oscillator

Grating stretcher

Compressor

1. PM-LMA fiber ampli.– High pump absorption– Polarized output beam

2. PCF-Fiber amplifier– High launch power– >800W pump power– Reduced non-linearities

Fiber amplifiers

ANR LAL / Amplitude Systemes

• > 300W average power• Linearly polarized beam

3D cavity

X

Y YX

Z

1

2

1

2

plane mirror

spherical mirror

plane mirror

spherical mirror

0 3D cavity

V1

V2

Low Loss Coatings : Ion Beam SputteringLow Loss Coatings : Ion Beam Sputtering

O2

Ar

Ar

O2

Ar

Targets

Quartz

Neutralizor

Neutralizor

- -

- -

SputteringSource

AssistSource

-++++

+++

- -

---

SputteredParticles

Substrate

++

++

++ -

---

Sample Holder(Simple rotation)

SiO2/Ta

4) Benchmark of the GEANT4 polarized version.

Knowledge & simulations

• POLARISED GEANT/EGS/NEW SOFT• CAPTURE• TARGETS

Baseline Target Design• Wheel rim speed (100m/s) fixed by thermal load (~8% of photon beam power)

•Rotation reduces pulse energy density from ~900J/g to ~24J/g

•Cooled by internal water-cooling channel

•Wheel diameter (~1m) fixed by radiation damage and capture optics

•Materials fixed by thermal and mechanical properties and pair-production cross-section (Ti6%Al4%V)

•Wheel geometry (~30mm radial width) constrained by eddy currents.

•20cm between target and rf cavity.

T. P

igg

ott, L

LN

L

Drive motor and water union are mounted on opposite ends of through-shaft.

Depolarization of positrons in bremsstrahlung

Initial Pol. Vs Energy of Captured Positron Beam

n. e+ x (rms)

mm

mrad

y (rms)

mm

mrad

<E> MeV

E/<E>

%

L (rms) mm

<3>

%

215 34 32 152.43 7.55 10.34 49.43

205 32 31 152.34 7.39 5.85 48.94

Beam parameters IIIParameters of the positron beam at the exit of the solenoid (z = 3085 cm) and of the Capture Section (z = 3436 cm)

Total capture efficiency ~ 2,05 %

Z= 3085

Z= 3436

Spot size of photon and positron

0.4 r.l. titanium target,Drift to target: from 10cm up to 500cm

Due to multi-scattering, positron beam spot size is bigger than photon beam spot size when photon beam is small.Due to lower probability of pair production from lower energy photons in the outer skirt of photon beam, the positron beam spot size is smaller than photon beam when photon beam spot size getting bigger.

Compton scattering & medical / industrial applications

• Extremely important : more and more fundamental science needs applications.

3 talks

• Jeff Rifkin• Sakae Araki• Philippe Balcou

Recommendations

• How to proceed.

ILC

• Baseline : need for E166 published result (V Important also for simulation benchmark)

• Find the common work topics (not an intellectual exercise …funding)

Attempt : Capture section (simulation and prototyping), target (repository as suggested by I. Bailey), Polarization generation, transport and manipulation.

• Alternative : Proceed towards STACKING simulations, Optimization,

explore the different schemes and converge to a single proposal => COSTING

CLIC : Definition of a “polarised” scheme with the new parameters. What could be a demonstrator experiment?

SuperB : New entry…to be supported.Evaluate the feasibility of a polarised solution

Recommended and supported R&D’s

Lasers & cavities:LAL : 200W fiber laser, 10exp4 gain cavity, 4 mirror cavity

at high finesse, full digitalized feedbackKEK (very important) : Cavity in ATF (very important)CO2 : demonstrator of intra cavity CO2 laser (dedicated

test stand, non linear optics, damages)Mirror damages @ High frep

Target : ILC demonstrator

Accelerators tech: High rep frequency and high charge per bunch e- guns

ALL this need coordinated effort of the POSIPOL community

Let’s add boxes…SuperB….

• Undulator :

• Ring :

• ERL:

• LINAC :

Thank you

And.. R.Chehab, A.Vivoli, F.Zomer, C. Eguren, B.Renard, Missions Service…..I surelyForgot someone

•And thank you to you all for participation

PosiPol 2008• Hiroshima Univ. proposes to hold PosiPol 2008 in

Hiroshima with support of KEK.

• The period will be May or June, which will be fixed later.

Hi

Hiroshima

KEK

Tokyo

Atomic BombMemorial Dome

ItsukushimaShrine

2 world heritages

• ILC Positron Source Group Meeting September 17 - 19, 2007Argonne National Laboratory

•   • The next ILC Positron Source Group Meeting

will be held at Argonne National Laboratory, Chicago, IL, on September 17 - 19, 2007.

• Please visit this site for more detailed information which will be posted in a few weeks.

• https://www.hep.anl.gov/ILC-positron