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Possible further extensions in thenew LEPS beamline in Spring-8

S. Daté Accelerator Division, SPring-8/JASRI

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LEPS Collab. MeetingAcademia Sinica, Jan. 13, 2006

S P r i n g8Contents

1. Introduction2. A short summary of previous discussions on energy u

pgrade above 5 GeV 3. A new estimate of high energy gamma yield for X-ray r

e-injection scheme4. Conclusion

S P r i n g8§1. Introduction

LEPS experiments have proved the accessibility to new frontiersin hadron physics by making use of its advantages in measuring the forward angular regions without harmful background noise and manipulating gamma ray characteristics through easy-to-access laser system. They also enjoy highly stable operation of Spring-8 accelerators and its low emittance electron beams. After 5 years of physics runs with several important outputs, we are in a position to discuss a new LEPS beamline with enhancement and emphasis of recognized advantages, supplements to weak points, and challenges to completely new possibilities, which all motivated by physics.

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SPring-8 Beamline Map

S P r i n g8Directions of extentions

Energy -> 3.5 GeV in near future (Laser upgrade) ~> 4 - 6 GeV ?Intensity -> 107-8/s (high power laser, LRNB, high current, round beam, new tagging system)Detector Polarized target

S P r i n g8High Energy Backward Compton Photons

S P r i n g8HELP production by X-ray re-injection

S P r i n g8HLEP generation by X-ray re-injection (2)

8 GeV 100 mA SR

Undulator

X-ray mirrorReflectivity = 0.810 = 10%

Ex =100 eV

E< 7.4 GeV

Diamond mirror

S P r i n g8Multilayer Reflectivity

S P r i n g8A short summary of previous discussions

X-ray generation reflection & re-injection gamma ray production

Gamma yield =

€

˙ N γ = 2Ie

e

σl

csR ˙ N ph = 4.16 ×10−12 Ie[A]

l[m]

s [mm2]Rσ [b] ˙ N ph

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d ˙ N ph

dωdΩ= αγ 2N 2 I

e

1

ωFk (K, γθ, φ;ω /ω1)

k=1

∞

∑

€

α I

e= 4.55 ×1016 (s−1) I[A]

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˙ N ph ≈4 ×1017 /s (100mA, N = 30)

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˙ N γ ≈ 2 ×104 /s×l[m]

s[mm2]R

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Cross section depends on photon energy

€

˙ N γ = 2Ie

e

l

csx

R ˙ I = 4.16 ×10−12 Ie[A]l[m]

sx[mm2]

R ˙ I

1 barn

€

d ˙ I

dEγ

= dωdσ

dEγ

(ω)ω1

ω2∫d ˙ N ph

dω

d˙ I dE/ I

e ,

S P r i n g8Re-focussing

Thin undulator approximation

e-

275x2 m

6x2 m

~100 rad

Can s be

€

5×10−3mm2 ?

In principle, yes.

spherical mirror

S P r i n g8Bunch 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

~Nγ

main

5

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Nγall ~ 1.75Nγ

main

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Bunch-bunch collisions

€

˙ N γ =ne / b( )

2

sfbRI 1

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I 1 = ˙ I Ie

e

=10−2 b (K = 5 ~ 6, Eγ = 4 - 6 GeV)

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s = 0.5 ×10−2 mm2

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ne / b fb =Ie

e

Limit: Heat load at finger contact ~

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ne / b( )2

fb

Maximum: 174 bunch filling

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˙ N γ = 2 ×106 /s × R

S P r i n g8Conclusion

Providedan undulator with high reflectable (R > 0.1)spherical mirror for 100 eV photonswith timing adjustment system (mirror position z = 24 +- 2 m, dz = 6mm)

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

We may obtain

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˙ N γ = 2 ×105 /s

in principle.

S P r i n g8*******LEPS/SP8 template******

S P r i n g8*******LEPS/SP8 template******

S P r i n g8*******LEPS/SP8 template******

S P r i n g8*******Suppl******

(2)

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˙ N γ = ne / b( )2 fb

sx

I 1

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=Ie

eI 1

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˙ N γ = 2I

e

σ l

csx

˙ N ph = 4.5 ×10−14 l[m]

sx[mm2]˙ N ph

S P r i n g8HELP generation (3)

S P r i n g8Primakov Production of

S P r i n g8Radiation formula

€

d ˙ N ph

dωdΩ= αγ 2N 2 I

e

1

ωFk (K, γθ, φ;ω /ω1)

k=1

∞

∑

€

α I

e= 4.55 ×1016 (s−1) I[A]

S P r i n g8Conclusion in the meeting on Oct. 20, 2005

The maximum yield of gamma in 5~6 GeV region attainable

in Spring-8 SR:

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2 ×104 /s×l[m]

s[mm2]

in an 1A, 1.5 GeV SR:

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3 ×105 /s×l[m]

s[mm2]

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K = 3, λ 0 =1.1 m

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K = 2.56, λ 0 = 5 cm

=>

=>

S P r i n g8Cross section convoluted with Nph

†

d˙ I dE

/ R/ I

e ,

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d ˙ I

dEγ

= R dωdσ

dEγ

(ω)ω1

ω2∫d ˙ N ph

dω

S P r i n g8An undulator to produce 100 eV photons

Matching of the first harmonics:

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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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λ0 <1 m

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⇒

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K = 3

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λ0 =1.1 m

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B0 = 300 kG

K > 2

S P r i n g8Yield of X-ray photons

†

d˙ N ph

d / I

e( 

      

      

      

      

      

      

)

S P r i n g8Compton cross section

S P r i n g8Reflectivity of N=11 multilayer mirror

S P r i n g8 Physics @workshop

Exotics: +, (1405), S11(1535) ---- 5q X(K-bound), C(1480) ---- 4q glueball, hybrid, odderon(odd-glueball) --- multi-g(+qq) Dirac monopole High precision: hyperon photoproduction nucleon resonance (e.g. pol +p 0 + p_pol ) A-dependence – mean free path nonmesonic decay of hypernucleus Compton scattering – nucleon swelling 0, –lifetime, polarizability, Primakoff (high E, forward) Others: J/ from d or A (c.f. Eth(+p J/ +p)=8.1 GeV) CP violation ()GDH polarized HD target