my view of nuclear photonics at eli-np with a 1st and 2

My View of Nuclear Photonicsat ELI-NP with

a 1st and 2nd Funding Period

Dietrich Habs Bucharest, Aug 18, 2011 1

D. Habs

LMU München • Fakultät f. PhysikMax-Planck-Institut f. Quantenoptik

a 1st and 2nd Funding Period

We need high-resolution γγγγ beam; examples: photofission + single resonancesPromising new physics

Development of much better diagnostics, detectors and γγγγ opticsNRF γ beam diagnostics, lenses, bent GAMS, LaBr3 detectors

Start now

Outline


Status of X-band SLAC e beam (Cecile Limborg)

Much better multi-bunches (20 pC, 180 ns), beam development requires time

(2013)

Improved layout of γγγγ beam for ELI-NP and experimentse.g. shift accelerator 2, longer γ beamlines

2 funding periods

1st phase: Eγ below Bn ~ 7.5 MeV; best technology available 2013

2nd phase: 2nd linac for highest γ energies; improved duty factor

Doorway state to shape isomers


Expected: 100 x stronger E1 in 2nd and 3rd minimum

Spectroscopy of transmission resonances in fission

γ spectroscopy of transmission resonances in 2nd & 3rd min.

Resonances with strong E1 will be important for transmutation of minor actinides.

Triple-humped fission barrierwith deep 3rd minimum (new paradigma)

For U istotopes the 3rd minimum is always 1.5 MeV deeper than predicted by Cwiok et al. (1994).

Also for Th isotopes we expect the 3rd

minimum 1.5 MeV deeper.

Experimental maxima and minima


P. Thirolf and D. Habs, Progress in Part. Nucl. Phys. 49, 325 (2002).

A. Krasznahorkay, Handbook of Nucl. Chem., Ch. 5, Springer, p. 282 (2011).

M. Csatlos et al., Phys. Lett. B 615, 175 (2005).L. Csige et al., Phys. Rev. C 80, 011301 (2009).A. Krasznahorkay et al., Phys. Lett. B 461, 15

(1999).

Experimental maxima and minima

Measured minima should be 0.3 MeV above potential curve.

New triple-humped barrier238U


Dickey et al., Phys. Rev. Lett. 35, 501 (1975).Goriely et al., Phys. Rev. C 79, 024612 (2009).Goriely et al., Phys. Rev. C 83, 034601 (2011).

TALYS reaction code;Goriely = standard input with wrong fission barriers and wrong level densities.

232Th triple-humped barrierHigh-resolution intermediate structure


Zhang et al. determined the ground state of the resonance to 2.8 MeV via level density,it was, however, not the 2nd but the 3rd minimum (which he assumed to be very shallow).

Zhang et al., Phys. Rev. Lett. 53, 34 (1984).J.W. Knowles et al., Phys. Lett. B 116, 315 (1982).

Intermediate structureHigh-resolution


WD = 100 keV = damping widthDIII = 2 keV ; BW ≈ 3×10-4DII = 2 keV ; BW ≈ 3×10-4DI = 10 eV ; BW ≈ 10-6

Excitation energy E above ground state from level densityRotational band 3rd min. E(2+) – E(1-) Rotational band 2nd min. E(2+) – E(0+)

keV 3.32

; keV 0.22

22

=Θ

=Θ IIIII

hh

PhotofissionPPAC detectors


Stack of fission detectors. Single target for measurement of angular distributions and mass distributions.

We will test the PPAC detector arrays at HIγS in 2012 and will develop high-rate more compact versions for ELI.

Doorway state Halo isomers


Halo isomers exist.1019 x more brilliant micro neutron beams.(patent Siemens – LMU).

New γγγγ diagnosticswith NRF and LaBr3 detectors

1st monitor beam size, central position for resonance energy (to eV) and to

µm in x and y.

2nd monitor beam direction in x and y in µrad and beam divergence in µrad.

Minimize scattering of non-resonant γs by collimators.

Shielded LaBr detectors have an energy window on the fluorescence line.


Shielded LaBr3 detectors have an energy window on the fluorescence line.

NRF wire targets or different size disk targets have precision diodes.

NRF diagnostics represent an indirect electron beam diagnostics to

optimize focusing, convergence, steering, beam diameter with high

accuracy.

Allows very accurate alignment of collimators with little loss of NRF signal.

Refractive γγγγ lensesfor focused and parallel γγγγ beams

Closely packed beamlet arrays of silicon lenses or stacks of single silicon

lenses are developed, starting from lower energies of 0.5 MeV.

While the individual electrons deliver their Compton γ energy-angle profile,

the overall electron beam with diameter and focusing translates into

focusing of the γ beam jointly with the γ lenses.


The γ lenses with their small diameter act as very precise collimators and

their focal length dependence on γ energy allows for γ monochromatization.

Refractive γγγγ lens (I)

2

RL


( )6

2

2

1070.2

2

−⋅=

∝=

A

Z

R

N

Rf LL

ρλδ

λδ

γ

γ

RL = radius of curvature ≈ R = radius of beamlet

Well established up to 200 keV, cheap, stable to vibrations

G. Vaughan et al., J. Synchr. Rad. 18, 125 (2011).

Refractive γγγγ lens (II)Nanofocusing lenses


Lenses made of silicon.

Ch. Schroer et al., APL 82, 1485 (2003).

Gamma lensesIndex of refraction and absorption

nuclear resonance

nuclear resonance


Si nanotechnology exists, extension from 0.2 MeV to several MeV.δ measurement at ILL in September 2011.

source

f = 2.3 m

FWHM = 4.4 µm

x y

RL = 2 µm parallel beam

Simple γγγγ-lens systemfor MEGa-Ray

E = 477.6 keV 7Li


10 × 2D circularLengler lensesRB = 1 mmRL = 0.3 mm

prefocusing system2.5 cm Al

1000 × 1D lensesRB = 30 µmRL = 12 µm

2×8.4 cm Si

x y

f = 2.3 m

collimator

Request: high brilliance, small opening angle

Result: dynamic monochromatization, parallel small-diameter beam, reduced intensity for detectors

γγγγ optics: large length (> 10 m), similar to hard x-rays, we can even get coherent γ-ray beams

Experiment: 478 keV ILL, 1.8 MeV HIγS

Eγ = 477.6 keV 7Li

γγγγ beam monochromatorsto 10-3 – 10-6 bandwidth

With bent crystal monochromators deflection of the γ beam with adjustable

10-3 to 10-6 bandwidth by about 1°is achieved, resulting in a very clean γbeam.

Even if typical nuclear transitions have a smaller bandwidth than 10-6 they

are Doppler broadened to 10-6. While for 7 MeV the high level density

requires a monochromatization to 10-6 for exciting a single level, for lower


requires a monochromatization to 10-6 for exciting a single level, for lower

energies less bandwidth is required.

We can reach efficient crystal monochromatization with parallel γ beams

from γ lenses and electron beam focusing. We need a long flight path to

transform γ beams.

The crystal system should be built at ILL with hardware (~ 0.4 M€) and

manpower (1 postdoc) with tests at ILL using special Doppler broadened

lines.

• Intensity is proportional to ratio of beam

divergence to FWHM of crystal acceptance

• Energy independent resolution:

– perfect crystals: FWHM ~1/E

(@1MeV≈10-8 rad)10-6 resolution independent of

Monochromatisationvia diffraction (M. Jentschel, ILL)


Collimation part must stay long

(@1MeV≈10-8 rad)

– diffraction Angles: ~1/E

(@1MeV≈10-2 rad)

• Energy dependent resolution:

– Crystals with finite acceptance: mosaic, bent/gradient

– typical FWHM: ≥ 10-7 -10-6 rad

– 10 – 100 times more intensity then perfect crystal

independent of Eγ possible

• Perfect crystal:

• Bent/gradient crystal:

Crystals(M. Jentschel, ILL)


• Mosaic crystal:

Rocking curve = Gaussian with FWHM of distribution of crystallites

Monochromating crystalsAngle interferometer

Double crystal monochromatorConcept for 10-6 resolution (M.Jentschel, ILL)


Pre-collimation(might not be needed for brilliant sources)

Collimation to separate diffracted from direct beam(minimum length: 3 meters)

Spectrometer table with Antivibration system

Material items (excl. manpower):

• Optics for interferometer*: 100 kEuro

• Heterodyne laser system*: 50 kEuro

• Phase reading electronics*: 50 kEuro

• Spectrometer mechanics: 100 kEuro

• Control Electronics: 50 kEuro

Double crystal monochromatorConstruction for 10-6 resolution (M.Jentschel, ILL)


• Control Electronics: 50 kEuro

• Set of strain free crystals*: 50 kEuro

Total: 400 kEuro

Manpower for design & construction:

• design office 100 kEuro

• engineer + technician 100 kEuro

• scientific consulting, overhead 50 kEuro

• Postdoc 2years 100 kEuro

Total: 350 kEuro

* Not needed for bent/gradient/mosaic crystal spectrometer

Energy Resolution of a 2.5mm Si220 @ 1.1 MeV

4.5 eV @ 1.1 MeV

Diffraction efficiency of a 2.5mm Si220 @ 0.8 MeV

22% @ 0.8 MeV

Performances of GAMSM. Jentschel (ILL, Grenoble)


LaBr3 ball1 – 2 MEUR

We should test part of the LaBr3 ball in the 1st funding period to learn:

Running with very high rate (fast digitalization)

Separating pile-up in time and space

After monochromatization only very few levels are excited and the low

multiplicity allows to build up level schemes with 10-4 resolution.


Such a system should be transported to MEGa-Ray to gain early experience.

In the 2nd funding period the ball should be completed to the full system.

SLAC X-bandGun development

Discussion of status report by Cecile Limborg at High Brightness workshop,

Daresbury, 29th of June 2011.

Promising new developments

Probably Chris Barty knows better.


SLAC X-band gun


New X-band RF gunLong-term


Reduced VrfPromising results


Conclusions For new electron beam

Future multibunches, 20 pC, macro pulse with 180 ns or longer;

presently the gun heats up by 50 °C, but future developments look

promising and lead to much improved electron beam.

Small bunch charge of 20 pC results in 1/100 CSR with easy deflection

of electron bunches


CW load of cavities results in much more stable acceleration fields;

expected bandwidth 10-4.

Similar to SLAC we need a good final diagnostics of the e beam

(emittance, energy spread, ….)

Layout ELI-NPMay 2011

2 ×APOLLON


Gamma beam + Electron beam

Layout ELI-NPAugust 2011


ELI-NP 1st funding periodγγγγ beam

Limit gamma beam energy to Eγ ≤ Bn ~ 7.5 MeV

Start new experiments on NRF and photofission at HIγS and MEGa-Ray

as soon as possible to reach a smooth transition to ELI-NP

Test the crystal monochromator at ILL

Perfom a test experiment on a positron source and gamma lenses at


Perfom a test experiment on a positron source and gamma lenses at

HIγS and MEGa-Ray and transfer the experiments to ELI-NP

ELI-NP 2nd funding periodγγγγ beam

Install the second electron accelerator reaching Eγ < 20 MeV

Install a new photogun with improved multi-bunch operation, longer

macro pulses, multiplexed clystrons (cheaper due to industrial

production) and more laser power

Install the electron beam to the high-field physics area


Install the electron beam to the high-field physics area

Positron source (I)NEPOMUC at reactor FRM II

9·108 s–1

103 e+/(s mm2 mrad2 0.1%BW)


New positron source much more brilliant

109 s–1

109 e+/(s mm2 mrad2 eV)

Hard γγγγ production

600 MeV electrons:

We study boosted frame with resting

electrons

Laser E×B field enhanced by 1200

Transform to reference frame with E = 0.


N. Elkina + H. Ruhl

Transform to reference frame with E = 0.

Mini synchrotron with very boosted

synchrotron radiation.

Micro γγγγ beam: 107 γγγγ/shot with 1 µµµµm diameter and up to 600 MeV.

Single crystal – resolution is defined by beam divergence:

h/L TOO LARGE for eV resolution

γ

θ

hc

E

hcnd =)sin(2

Gamma ray spectroscopywith a double crystal spectrometer (M.Jentschel, ILL)


( )

γ

γγγ

γ λλ

λθ

θ

E

hcFWHM

hcEAy

y

yAR

2

,,

1

1sin)(

2

22

=

=∝∝

+

+∝

FWHM

γ

θE

hcn≅

Double Crystal Spectrometer:

• First Crystal defines beam axis with nrad

• Bragg Angle is measured @ second crystal

• Resolution is energy independent

• Resolution: ∆E/E ~ 10-6

~ 10 nrad

~ 1 mrad

Real part of refraction indexTheory (I)

Kramer Kronig dispersion relation: ( ) ( )∫∞

−+==

0

22

med

vac ..1ωωωωα

πλλ

ωa

aa dPPc

n

( )

( )( )

( )22

0

22

tot

02

2

-1

lim2 )scattering forward(coherent

][cmt coefficien absorption

Ai

d

cd

df

a

aa

a

ωεωω

ωσωπωσ

ωα

ε=

+−⋅=

Ω

=

∫∞

→ +


( )( ) ( )

22

2

2

2

0

2

0

137

1 ; 2 fm MeV 197 ; fm 8.2

:constants Some

scattering forwardcoherent for amplitude

per volume centers scattering ofnumber ;h wavelengt2

21

2

mcmc

EE

c

ehc

mc

er

A

N

ANn

icd

f

f

a

ω

απ

π

ωπω

εωωπ

γ h

h

D

D

==

==⋅===

=

==

⋅⋅=−

+−Ω

Real part of refraction indexTheory (II)

scatteringDelbrück effect creation pair virtual73

effectCompton virtual ln3

8

scatteringRayleigh effect photo virtual corr. rel.

0

2222

20Compt

0photo

==+=

=−=

==+−=

rZEA

EEr

A

ZrA

απ

πα


( )( )

resonanceWigner -Breitnuclear

scatteringDelbrück effect creation pair virtual21152

73

22nucl.res.

2

0pair

=⋅Γ+−

Γ⋅−=

==+=

E

hc

EE

EEA

rZEA

r

r

παπ

J.S. Toll, “The dispersion for light and its application to problems involving electron pairs”, thesis, Princeton 1952.

S. Klein, “Suppression of bremsstrahlung and pair creation”, Rev. Mod. Phys. 71, 1501 (1999).

my view of nuclear photonics at eli-np with a 1st and 2

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