measurement of the capture cross section of cm & cm€¦ · simon2 monitor •stable monitor...

Measurement of the capture

cross section of 244Cm & 246Cm1V. Alcayne, 2A. Kimura, 1E. Mendoza, 1D. Cano Ott

and the n_TOF Collaboration

1CIEMAT– Spain2JAEA – Japan

n_TOF CM | V. Alcayne | 27. Nov 2018 | 2

Introduction

Measurement during May-September 2017

Second smallest capture mass (177Tm ~0,3mg)

Second capture measurement in EAR2.

Precise background subtraction is needed

Sample ~1 mg with ~2 GBq activity

→Physics case for EAR2

TAC in EAR1TAC

Lower intensity / 185m flight

Better RF

Information EM cascade

C6D6 in EAR2 TED

High intensity / 20m flight path

Worse RF

Data processing

• Reprocessed data

New Pulse Shape

Rebounds study

• New MC simulations

Full setup simulation

Energy Calibration

Energy Resolution

Gain Drift

Reproducing MC

simulationsLink to Analysis meeting talk

https://indico.cern.ch/event/735668/contributions/3047479/attachments/16834

68/2705906/PresentacionCm244NTOF7_18v05.pdf


https://indico.cern.ch/event/735668/contributions/3047479/attachments/1683468/2705906/PresentacionCm244NTOF7_18v05.pdf

https://indico.cern.ch/event/735668/contributions/3047479/attachments/1683468/2705906/PresentacionCm244NTOF7_18v05.pdf

n_TOF CM | V. Alcayne | 27. Nov 2018 |

SiMon2 Monitor

• Stable monitor for 3 months

105 µg/cm2 ->Li6

4 silicon detectors 300µm

• New MC simulations

Full setup simulation

Energy Calibration

Energy Resolution

Gain Drift

Reproducing MC

simulations

4

Normalization with SiMON2

WONDER 5th| V. Alcayne | 10. Oct. 2018| 3

Flux calculated with SiMon2


Small differences

1-2%

• Corrected by:

Detector efficiency

XS convoluted with RF

using Transport Code

Flux calculated with SiMon2

7

Monitoring Run by Run

Differences sample position

Effective gain control of C6D6

Normalizing to SiMon2

Other effects

8

Differences sample position

Effective gain control of C6D6

Normalizing to SiMon2

Other effects


Small differences

1-2%



244Cm EAR2

11


246Cm EAR2

12

n_TOF CM | V. Alcayne | 27. Nov 2018 |

Geant4 Simulations

Percentage of counts

lost below the threshold

(0.12 MeV)244Cm 7.2%246Cm 9.9%240Pu 4.4%197Au 4.1%

13

Preliminary WF Det1


Preliminary capture yields


Outlook and Summary

TAC in EAR1

• Alpha discrimination

• Calibration

• Coincidences

• Reproduction Cascades

• Efficiency TAC (MC

Simulations)

• Resolution function and

corrections

• Normalize to neutron flux

• Analysis with Sammy

• ….

C6D6 in EAR2

• Calibrations

• Gain drift corrections

• PSA routine

• Background calculation

• Normalization to neutron flux

• WF

• Cascade Simulations

• Gain variation as a function of

the TOF

• Coincidences between detectors

• Resolution function and

corrections

• Resonance analysis

• ….


Hola que tal

BACKUP SLIDES

Small differences

1-2%


M. S. Moore and G. A.

Keyworth, Physical

Review C, 3, 1656 -

1667 (1971)

Experiment by Moore et al. Experiment by Kimura et al.

Only 2 sets of previous data

A. Kimura et al., J. Nucl.

Sci. Tech. 49, 708

(2012).

1969 Using underground nuclear

explosion

Moxon-Rae detectors

Accuracy questionable due to

systematic uncertainties

No data under 20eV

2010 at J-PARC

Two cluster-Ge detectors

Above100 eV, the measurement required

severe dead time corrections (up to 90%)

Resonance analysis up to 30 eV

Samples

Two 244Cm sample

(%)246Cm sample (%)

244Cm 60.6±1.1 (~0.80 mg) 20.3±0.5 (~0.38mg)245Cm 2.38±0.30 (~0.02 mg) 1.03±0.29(~0.02 mg)246Cm 6.35±0.55 (~0.08 mg) 57.7±1.5 (~1.10mg)247Cm ----- 2.8±0.4 (~0.05mg)248Cm ----- 8.8±0.2 (~0.17mg)240Pu 31.1±0.6 (~0.40mg) 9.30±0.15 (~0.17mg)

9cm

Cm

9mm5mm

0,5mm 1,2mm

Cm

MylarKapton Al Ring

C6D6 Setup EAR2 (~20 m)

Neutron Beam

Sample

• Experiment

3 months.

8·1018 protons of 20 GeV/c.

~ 50% of the beam measuring 244Cm and 246Cm rest dummy

measurements and check.

• Three detectors

Efficiency proportional to energy (egi∝Egi )

achieved using PHWT.

Good time resolution (~1ns).

• Analysis

Precise background subtraction.

Energy calibration (133Ba, 137Cs,60Co, 88Y, AmBe and CmC)

Gain drifts (12 sets)

244Cm Experimental results EAR2

246Cm Experimental results EAR2

TAC Setup EAR1 (~185m) • TAC( Total Absorption Calorimeter).

Sphere of 40 BaF2 crystals, 95% solid angle.

Detecting almost all the gammas in the cascade.

• Experiment

2 weeks.

5·1017 protons of

20 GeV/c.

• Analysis

Coincidence between

the 40 detectors. Reject background.

Montecarlo simulations with Geant4.

244Cm Experimental

results EAR1 TAC

EM cascades TAC

• Background subtracted

• Different multiplicities

• Normalization

~60000 counts

~300000 counts

Hola que tal

Motivation

Hola que tal

Neutrons per Pulse at n_TOF

~5*104 neutrons

~2.5*106 neutrons

• 6 sources used( 133Ba,137Cs,60Co,88Y,AmBe,CmC)

• Fitting MC simulation with χ2

Energy calibrations

𝑓(𝑥) ቊ𝑎𝑥2 + 𝑏𝑥 + 𝑐 𝑥 < 𝑥0𝑑𝑥 + 𝑐 𝑥 ≥ 𝑥0

• 6 sources used( 133Ba,137Cs,60Co,88Y,Ambe,CmC)

• Fitting MC simulation with χ2 method varying gain and

resolution.

Energy resolution

n_TOF AM | V.Alcayne | 10. July. 2018 | 42

Gain Drifts

• 10 calibration measurements

• Source always in the same

position.

MC Simulations Source Response

44

CALIBRATIONS

measurement of the capture cross section of cm & cm€¦ · simon2 monitor •stable monitor...

Documents