physics at eli-np: towards tdrs for nuclear resonance ... · july 2012 | norbert pietralla @ cssp...

2. July 2012 | Norbert Pietralla @ CSSP Sinaia | Physics @ ELI-NP: NRF from the S-DALINAC towards ELI

Physics at ELI-NP:

Towards TDRs for Nuclear Resonance

Fluorescence and electron scattering

Norbert Pietralla + group, TU Darmstadt

DAAD BMBF

DAAD

293 MEuro approved: Congratulations!


< 18 MeV -ray beam from LCB


Outline

Nuclear physics with low-energy photons (observables)

Recent experiments at Duke‘s HIS

NRF count-rate estimate for ELI-NP

Sketch NRF TDR (based on HPGe + ancillaries)

Nuclear physics with electrons (e,e‘)

Recent experiments at Darmstadt‘s S-DALINAC

(e,e‘) count-rate estimate for ELI-NP

Sketch (e,e‘) TDR (based on S-DALINAC‘s Q-CLAM spectrometer)

Summary


Photonuclear Reactions

What happens?


Photonuclear Reactions

gs

´

Separation

threshold

AX

A´Y

Nuclear Resonance Fluorescence (NRF)

Photoactivation

Photodesintegration

Absorption

(-activation)

´

~ 8 MeV

2. Sept. 2012 | Norbert Pietralla @ 6th Tours Symposium | Photonuclear Physics: From the S-DALINAC to ELI

Nuclear Resonance Fluorescence

Separation

threshold

Observables

• Excitation Energy Er

• Spin J

• Parity p

• Decay Energies E

• Partial Widths Γi/Γ0

• Multipole Mixing d

• Decay Strengths B(pl)

• Level Width Γ (eV - eV)

• Lifetime t (ps – as)

NRF Theory Background and Facts

Widths of particle-bound states: 10 eV

Single-spin level density: J 104 MeV-1

→ isolated resonances

QM:

Decay law:

Typical lifetime limit: t 100 as

Total width:

Transition rates:


NRF cross section

Breit-Wigner absorption resonance curve for isolated resonance

[from Fourier transform: (t) (E) ]

0/

On resonance cross sect.s can be very large: 0 200 b (for 0=, 5 MeV)

However, resonances are very narrow

Thermal motion of target nuclei leads to Gaussian Doppler-broadening of

resonance (typical Doppler width few eV 100s of meV)

Energy-integrated cross section: 0


Scattering cross section


Isc,0 = Ia 0/ 02/

N. Pietralla et al., Phys. Rev. C, 51, 1021 (1995).

Angular Distribution, Spin Quantum Number J

Photon helicity 1, m = 1

non-isotropically alignment of

photo-excited state

(even oriented for circularly

polarized beam)

Pronounced angular correlations

when involving spin-0 states

Angular distribution functions W()

from angular correlation theory

Spin quantum numbers J

(easiest in even-even nuclei). 2. Sept. 2012 | Norbert Pietralla @ 6th Tours Symposium | Photonuclear Physics: From the S-DALINAC to ELI

90o/127o – intensity ratios: 2.0 (J=2) vs 0.8 (J=1)

Parity quantum number p for J=1 states

Elastic scattering distribution not isotropic about incident polarization plane.

No intensity along oscillating dipole vector

Azimuthal rotation by 90o for M1 and E1 distributions

Observable only for linearly polarized beam


Linearly-polarized photon beam:

Parity measurement by azimuthal distribution


NRF – Set-up and parameters

Count rate estimate

104 /(s eV) in 100 macropulses

100 /(s eV) per macropulses

Example: 10 mg, A 200 target

Resonance width = 1 eV

2 excitations per macropulse

0.5 photons per mac.p. in detector

PP-count rate 6 Hz

1.000 counts per 3 min.

E.g. 252Cf, T1/2 = 2645 a

10 mg = 100 MBq (E=43 keV)

Backgrd. count rate 100 kHz/det.


8 HPGe detectors

2 rings at 90o and 127o

rel(HPGe) = 100%

Solid angle 1p

Photopeak PP 3%

Costs: 1.460 kEUR

target

HPGe

Last week‘s example: 31P


Christopher Romig, TU Darmstadt

Data taken at HIS, 09/27/2012

50% P2O5

J=1/2

Jp=3/2+

TDR NRF – Set-up

8 HPGe detectors (100%ers, + BGO-shields, 160 kEUR each)

Frame, mechanics, cabling (100 kEUR)

HV supply, digital DAQ (50 kEUR)

LN2-supply (30 kEUR)

Total: 1.460 kEUR

Ancillary particle detectors (for (,p[‘])-reactions)

1 x 15 cm DSSD-“CD“ (8 rings x 8 sectors, backward cap, 20 kEUR)

8 x 10 x 10 cm2 DSSDs (10 x 10 strips, „target barrel“, 70 kEUR)

HV supply, digital DAQ (180 channels, 250 kEUR)

Sub-Total (ancillary-only): 340 kEUR

This will make entirely new reaction possible, partic., on isotopes with Sp < Sn

Total TDR: 1.800 kEUR, established technology, ready on day-one


doesn‘t make it all

Momentum transfer

ELI – NP has a superior electron

beam for nuclear structure

research (200 – 700 MeV,

E/E 10-4)


(,‘): d/d(E)

(e,e‘): d/d(E,q)

Virtual-photon scattering

(= electron scattering) decouples

energy and momentum transfer

Electron sensitive to form factor

charge distribution

Charge (and magnetization)

distributions sensitive observable


Electron and Proton Scattering on A = 90

O.Burda et al., Phys.Rev.Lett. 99, 093502 (2007)

One-phonon states are strongly excited in

(e,e‘) and (p,p‘) scattering experiments

S-DALINAC data

• Typical beam current: 5 A

• 10 mg/cm2 target

• Elastic line: 20 Hz

• Total rate: 100 Hz

• E/E = 4 10-4

Experimental setup

25. Mai 2012 | Institut für Kernphysik | TU Darmstadt | Abdulrahman Scheikh Obeid | 4

Spectrometer


Recent example 92Zr



Transition Form Factors for 92Zr

Diffraction pattern in (p,p‘) shifted to higher momentum transfers for MSS

MSS has smaller matter transition radius than FSS! p-n-phase?

C.Walz,… NP,… et al., Phys. Rev. Lett. 106, 062501 (2011)

S-DALINAC data


Transition Form Factors for 92Zr

Diffraction pattern in (p,p‘) shifted to higher momentum transfers for MSS

MSS has smaller matter transition radius than FSS! Access p-n-phase!

C.Walz…NP… et al., Phys. Rev. Lett. 106, 062501 (2011)

S-DALINAC data

Model-independent extraction of E2 excitation

strength

< 3% negligible

Expansion in momentum transfer


Example: Darmstadt Q-CLAM spectrometer


Count-rate estimate

Arguments for (e,e‘) @ ELI-NP

Complementary energy range

150 – 700 MeV

ELI-NP competitive resolution

Timing ideal for coincidences

„parasitic“ experiments easily

possible

Optimize spectrometer


S-DALINAC (E < 130 MeV)

Typical beam current: 5 A

10 mg/cm2 target

Elastic line: 20 Hz

Total rate: 100 Hz

E/E = 4 10-4

ELI-NP e-beam

Ie 5 A

in 100 x 1000 microbunches

On average 1 ct / macrobunch

At least < 5 cts / macrobunch

No pile-up

No deadtime

TDR (e,e‘)

Allocate space for (e,e‘) !

Evtl. optimize e-beam dump

Beam lines and valves: 130 kEUR

Scattering chamber: 50 kEUR

Pre-collection quadrupole magnet: 70 kEUR

Large-gap dipole magnet: 2 MEUR

Wire chambers for e-tracks: 400 kEUR

Cherenkov counter: 150 kEUR

Vaccum needs: 100 kEUR

DAQ: 200 kEUR

Total needs: 3.1 MEUR



Summary

Nuclear dipole physics with -ray and e-beams is a vivid field

ELI-NP will become the ultimate NRF facility

Established technology, ready from day-one

Join the NRF@ELI-NP working group!

ELI-NP can be a highly competitive electron facility, either.

Technique fully developed: buy from the shelf


Thank you !

physics at eli-np: towards tdrs for nuclear resonance ... · july 2012 | norbert pietralla @ cssp...

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