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Nuclear Physics – abstracts
Project Title Research Group
Contribution to the performance of an experiment at the Tandem accelerator

At the Tandem accelerator a typical experiment takes about one week. As our accelerators are operated by students and PhD students, you can learn how the accelerators are operated and participate in three different nuclear physics experiments, including doing the on-line analysis.

Analysis of nuclear physics experiments

The analysis of a nuclear physics experiment takes quite some time and includes calibrations, corrections for shifts and fitting the data. During the internship you will learn how  one of these tasks is done and then work on real data. Thereby you will contribute to the analysis of a experiment. The subject depends on the research needs at the time of the internship.

Construction and testing of detectors and set-ups

Most nuclear physics instruments are unique of its kind and need to be constructed by our mechanical and electronics work shop. Together with one of our physicists you will be involved in this process. Which instrument you will be working on depends on the research needs at the time of the internship.

Simulating experimental situations

Before performing expensive experiments and/or constructing new instruments Monte Carlo simulations are done. Their aim is to optimise the lay-out of the instrument or the beam intensity and purity of a rare isotope beam, i.e. at GSI. During the research internship a program for simulations will be introduced and then applied to a concrete case. The subject depends on the research needs at the time of the internship.

Testing and improving of a particle-gamma coincidence setup

A new coincidence setup consisting of gamma and particle detectors is installed at the tandem accelerator at the institute for nuclear physics. This system is equipped with a fully digital readout. Due to these developments, unprecedented experiments can be performed in the near future to investigate problems in nuclear structure or nuclear astrophysics. The goal of this research internship is the testing of different detectors and the installing of improvements.

Contribution to the conduction and analysis of experiments at the Cologne tandem accelerator

In order to study the structure of atomic nuclei or to investigate the open questions in nuclear astrophysics, many experiments are conducted at the Cologne tandem accelerator. Both performing these experiments and analysing the data can be part of this research internship. In the former case, experimental work needs to be done in the accelerator area of the institute. In the latter case, the main focus is on the analysis of spectra, performing theoretical calculations, and programming analysing codes.

Investigations of Plunger foils under bombardment with a heavy ion beam

The recoil-distance method (RDM) is a standard technique to measure level lifetimes of excited nuclear stated in the range of ≈ 5x10-13 s up to ~ 1 ns. The nuclei of interest have to be produced by an in-beam nuclear reaction in a target. Due to the transferred momentum, the nucleus of interest leaves the thin target foil with a velocity v and is stopped after a defined flight time in an additional foil, called stopper, placed downstream of the target.  The excited nuclei cool down by gamma emission. Those gammas which are emitted during flight are Doppler shifted and those which are emitted in the stopper show the original energy. In a spectrum measured by a Ge-Detector at zero degrees with respect to the beam axis one observes two components from which the lifetimes can be determined. In order to use this technique a so called plunger device is needed
The Plunger apparatus is a mechanical device which allows for a precise adjustment of two foils, the target and the stopper foil, parallel to each other and for setting a well defined target-to-stopper separation down to values in the micrometer range.   The precision of the settings should be in the micrometer or sub-micrometer range for recoil velocities of about 1%-3% of the velocity of light which are typical values obtained after a fusion reaction, e.g. 16O, 28Si or 32S induced reactions.  In such cases a flight time of 1ps corresponds to travel distances of 3-9 μm.

The topic of the research internship is the investigation thin metal foils under bombardment with a heavy ion beam. Especially we are interested in the:

- Deformation of stretched foils introduced by the beam pressure
- Deformation of the foil caused by beam heating
- Determination of absolute separations of two stretched foils using the capacity method 

The Measurements will be done at an ion source test bench. The deformations will be measured by measuring the capacity of the two metal foils.


Statistical analysis of AMS data measured at Cologne AMS

CologneAMS is a new centre for Accelerator Mass Spectrometry (AMS) at the University of Cologne.  The AMS-facility is designed for the spectrometry of all standard cosmogenic nuclides like 10Be, 14C, 26Al, 36Cl, 41Ca, 129I and in addition to measure sensitively heavy ions up to 239U and 244Pu. The device is suited to measure extreme isotope ratios, down to ~10-16, e.g. for 14C/12C or 10Be/9Be. It consist of a low energy mass spectrometer with a negative ion sputter source, a 6 MV TANDETRON accelerator followed by a high energy mass spectrometer with two detection systems for the radioactive isotopes. In addition a further AMS system is being installed at the 10 MV-tandem-accelerator which is operated by the institute of nuclear physics.   

We offer a research internship which is closely related to the above described facilities.
The following topics should be covered:
Investigation of AMS-Data which has been measured at CologneAMS with respect to various statistical properties:

- correlations
- fluctuations
- unusual behaviour of individual samples
- detection of outliers

The information gained from such an analysis is of special interest because it might be useful to improve the quality of the final results.

Expected knowledge: Basic skills in statistics,
Skills in programming would be advantageous but are not obligatory.