Grupo Experimental de Núcleos y Partículas

DESCRIPTION

β decay half-lives and nuclear structure of heavy  neutron-rich nuclei produced by ²⁰⁸Pb fragmentation

This experiment aims to reach, by means of gamma and beta ray spectroscopy, a detailed knowledge on the structure and half-lives of heavy neutron-rich nuclei, near to the neutron closed shell N=126 and produced in the fragmentation of ²⁰⁸Pb primary projectiles.

These measurements will provide valuable information not only about nuclear models far from stability, but also about the interpretation of the observed r-process abundances.  The last one is of special interest in nuclear astrophysics due to the rapid neutron-capture process (r-process) of nucleosynthesis is thought to be the medium of creation of half of the elements heavier than iron.

The experiments are performed at the SIS synchrotron accelerator at GSI which delivers the ²⁰⁸Pb beam with an energy of 1 A GeV. The beam impinges into a Be target and the heavy neutron-rich nuclei produced by cold-fragmentation reactions are isotopically identified by using a magnetic spectrometer Fragment Separator (FRS). The fragments produced are implanted into an active stopper in order to measure their structure and half-lives from position-time correlations between the implanted fragments and the consequent β and γ decays.

PARTICIPANTS

Participants

A. Morales

S. Verma

D. Pérez

H. Álvarez

E. Casarejos

J. Benlliure

P. Regan

Z. Podoyak

S. Pietri

S. Steer

G. Farrelly

A. Denis

A. Bruce

F. Molina

J. Agramunt

B. Rubio

A. Algora

M. Gorska

P. Doornenbal

H.J. Wollersheim

J. Gerl

S. Tashenov

L. Cáceres

P. Boutachkov

B. Gelletly

A. Gadea

J. Grebosz

D. Cortina

D. Dragosavac

Shift Plan for S312 experiment

Team members

A:  David, Plamen, Steve, Pancho
B:  Anabel, Pieter, Alejandro
C:  Shashi, Lucía, Gregory, Dusan
D: Héctor, Stanislav, Ana, Jorge

People on call

Pepe, Enrique, Stephan, Magda, Zsolt, Lola

Supervisors

Hans Juergen, Berta, Juergen, Paddy, Bill, Alison, Andrés

"Experts"

FRS:  Pepe, Enrique, Magda, Zsolt, Lola
DAQ:  Stephan, Henning, Nik
ON-LINE:  Jurek, Stephan
Silicon Detectors: Stephan, Jorge, Pancho
RISING: Stephan

TECHNICAL INFO

Technical Information

Filesheet (PDF)

Filelist (XLS)

Experimental Setup

FRS ion optics

Targets & Degraders

Detectors and electronicsi (Voltages).

• MW (Calibration Parameters)
• Scintillators
• MUSIC (PDF file)

Data acquisition

• MBS
• DAQ handling
• Online analysis (Go4,SATAN)
• Parameter list

FRS handling

• Before starting (loading ion-optical files, starting different programs ??)
• Setting the FRS (loading a reference setting and scaling)
• Saving a setting
• different programs  SD, DI, setting current grids, change the seetram sensitivity...etc...??)
  How to get the status of all devices in the beam line

SEETRAM calibration

S312 Targets and Degraders

Overview

TA Area

S2 Area

S4 Area

* Total equivalent Al thickness of S4 = 3727.44 mg/cm2
* Equivalent Al thickness till end of DSSD2 = 3141.64 mg/cm2
* Equivalent Al thickness of 1mm of Si = 238.36 mg/cm2
* Equivalent Al thickness from 0.5mm of DSSD1 to the surface of SC43 = 440 mg/cm2

Setup at S0

• SEETRAM (13mg/cm²)
• Target (1624 or 2513 mg/cm²
• Nb foil (221 mg/cm²)

Setup at S2

S2 DEGRADER SETUP

Setup for the 1624 mg Be target. (Projectile: ⁴⁰Ar , setting centered in ³⁴Al).

Projectile: ²⁰⁸Pb @ 1 GeV/u

Sc21 and Nb foil @ S2 positions

Detailed degrader settings @ S2 and ToF range estimations

Web calculator of Degrader S2 elements.

• Scintillator (3 mm , eq. to 379.42 mg/cm²)
• Degrader
• Nb foil (106.88 mg/cm² , eq . to 88.38 mg/cm² Al )

Setup at S4

• Scintillator (3 mm , eq. to 379.42 mg/cm²)
• MUSICs
• Degrader
• DSSD Silicon Detectors

Detector settings for S312

Current grids

MUSIC chambers (MUNICH)

Scintillators

MultiWire PCs

MultiWire PCs Calibration Parameters

Parameter List

• FRS Crate
• Stoppers
• Germanium detectors

Loading ion-optical calculations

On AXP316 (Program SD):

Change of FRS setting

Program SRMAG:

Choose the FRS section to be scaled (program MGSKAL):

Scale the section (program MGSKAL):

goto number 3 until all FRS is scaled.

print the magnet status (program SD):

Save of FRS setting

Use program SRMAG:

FRS Calibration

• Calibration Protocol (PDF file)

Calibration Settings:

Settings

⁴⁰Ar @ 300 MeV/u

²⁰⁸Pb @ 1 GeV/u

For the values of the scaling factors:

In case of problems:

• Plug the beam dump (TS3SV2)
• Load the new Reference Setting with SRMAG program
• Scale by 1.000 from Target to S4 with MGSKAL program
• Check the B values, remove the beam dump and go on

ANALYSIS INFO

MAIN RESULTS