Medium and High Energy Photons for Nuclear Particle

Physics

Schin Daté Accelerator Division, SPring-8/JASRI

Advanced Photons and Science Evolution 2010 June 14-18 , 2010, Osaka Japan

Previous talks which includes laser backscattering

beamlines

T. Shima: New Subaru

Y. Ohashi: LEPS/LEPS2W. Tornow: HISW.C. Chang: LEPS

M. Niiyama: LEPS/LEPS2

My talk:

I. High Energy Production in SPring-8

II. Intense 10 MeV Production in Light Sources

Additional options to future backscattering beamlines

Production of high energy gamma rays

HELP production by X-ray re-injection

multilayer mirror

Choice of Undulator

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K = 0.934 × B0[T]λ 0[cm]

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100 eV = ω1(0) = 4πβhcγ 2 /λ 0

1+ K 2 /2

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Ptot ~ Nγ 2K 2 /λ 0

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K 2

(1+ K 2 /2)2Portion of the fundamental=

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λ0 <1 m

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K = 3

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λ0 =1.1 m

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⇒

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B0 = 300 kG

Yield of X-ray photons

†

d˙ N ph

d /I

e(  

      

      

      

      

      

     )

Re-focussingThin undulator approximation

e-

275x2 m

6x2 m

~100 rad

Can s be

€

5×10−3 mm2 ?

In principle, yes.

spherical mirror

Bunch mode dominance

. . .100 rad

60 cm

h ~ 275 m

e-

v ~ 6 m

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60cm/2 ×100μrad = 30μm

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Nγnext ~ σ

aph

~ Nγmain

5

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Nγall ~ 1.75Nγ

main

Yield of High Energy Gamma

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L=neN ph

sRfbunch

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€

I 1 ≡ Nph

1 ⊗σ

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N ph = neN ph

1Notation: ,

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I 1 =10−2 b

Undulator (K=5~6, λ =1.1 m, 4 periods)

: reinjection efficiency

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R

for

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Eγ = 4 - 6 GeV

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⇒

Electron beam emittance + re-focussing

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s = 5 ×10−9 m2

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εx = 3.4 ×10−9 m⋅rad( )

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⇒

Beam current: 100 mA/e

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ne fbunch =

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⇒

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( ≈ )

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Nγ ≈106 /s.

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Nγ = L ⊗σ ,.

50%

Summry of part IProvidedan undulator with high reflectable (R > 0.5)spherical mirror for 100 eV photonswith timing adjustment system (mirror position z = 24 +- 2 m, dz = 6mm)

€

N p = 4, λ 0 =1.1m, B0 = 300 kG − 600kG

We may obtain

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˙ N γ =106 /s

in principle. The number may increase by an order of magnitude forthe future refinement of the storage ring.

Intense 10 MeV Production in Light Sources

II

Well known facts about Compton back scattering

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E e

€

εL

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Eγ

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θ

Controlled Polarization(3)€

dσdEγ

~ flat(1)

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εL ≤ Eγ ≤ Eγ max ≈ 4γ e2εLEnergy ,

Angle

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θ =θ(Eγ )

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<θ 2 >≈1/γ e2(2) ,

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˙ N γ = 2.1×107(s−1)σ [b]I[A]λ L[μm]l[m]PL[W ]/sL[mm2]

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=1.34 ×108(s−1)PL[W ]

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σ = 0.5 bI = 100 mA

l = 10 m

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sL = π (0.5 mm)2

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λL =10 μm

€

for

Yield(4)

Progress in laser technology

Heat load limit ~ 20 MW / mm 100 kW output is cleared in this way

bundled fiber line of, say, cm is possible to make

Fiber Laser

Sing

le m

ode

CW

out

put p

ower

(W)

year

15m core

Yb fiber laser (IPG): 1030 ~ 1050 nm CW single mode 2 kWmultimode 20 kW

Polarization?

Eg_max for CO2

2. Production of Intense 10 MeV Rays

(1) Enegy aperture

Spring-8 CLS DFELL MAX-IV NSLS-II

8 2.9 0.24-1.2 3 3

2436 285 64 96 1320

16 0.876 42 keV 0.712 0.816

4/3 2.74 17.1 1.7 4.04

154 4519 @ 500 MeV30 @ 1.2 GeV

91 91

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E0 [GeV]

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h

€

α

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U0 [MeV]

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q

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δEmax[MeV]

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1.68 ×10−4

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3.8 ×10−3

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8.6 ×10−3

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7.45 ×10−4

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3.7 ×10−4

(2) Longitudinal beam quality

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˙ N γ =

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1011

€

s−1

I = 100 mA

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⇒

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Pγ / e− pass =10−7

Spring-8 CLS DFELL MAX-IV NSLS-II

4.8 0.57 0.36 0.96 2.6

4.2 1.9 4.3 4 9.7€

T0(μs)

€

α s−1(ms)

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107T0 >> α s−1

No serious effect on the longitudinal beam quality

Summary of Part II

There is no crucial problem to producee very intense (~ 10^11 /s) 10 MeV gamma rays in 3 GeV light sources including CLS, MAX IV and NSLS-II..There are technologies available to realize the intense gamma production.Now is the adequate time to consider such a possibility seriously.

Conclusion

I. We may think seriously about quasi-monochromatic g beamline with Eg_max ~ Ee and Ng ~ 10^6 /s as an option to future beamlines in highenergy synchrotron light sources.

II. There is no crucial problem to producee very intense (~ 10^11 /s) 10 MeV gamma rays in new 3 GeV light sources.

-------- Backup --------

reinjection schemes

Why Do We Want 10^11 /s Photons?

= 10 g / cm^3

Because many interesting elementary interactions occur with σ ~ pb

l = 1 cm

σ = 1 pb €

N l = 6 b−1

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⇒

€

⇒

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˙ N γσρl = 0.6 s−1

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˙ N γ = 1011 s−1for

S P r i n g8

Old proposal

Optical param bl33

optical parameters

beam divergence

<σ x’ >BCS ~ 64 rad beam divergence in LSS BL is dominated by Compton scattering.

εx = 3.4

€

×10-9 rad

€

⋅mεy

εx, = 0.2 %( )

<=

33LEP LSS<σ x’ > [rad]

58 23

<σ y’ > [rad]

1.8 1.2

<σ x > [mm] 0.34 0.30<σ y > [m] 12 12

<=>

Contributions are wighted for Gaussian laser beam.Values are valid for the laser waist radius > 0.5 mm.

Angular Distribution

Polarization

Energy

E (GεV)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

00 .5 11 .522 .5 3