Heavy Ion Physics

Abstract

Calorimetric low temperature detectors have the potential to become powerful tools for applications in many fields of heavy ion physics. A brief overview of heavy ion physics at present and at the next generation heavy ion facilities is given with a special emphasis on the conditions for heavy ion detection and the potential advantage of cryogenic detectors for applications in heavy ion physics.

Two types of calorimetric low temperature detectors for the detection of energetic heavy ions have been developed and their response to the impact of heavy ions was investigated systematically for a wide range of energies (E = 0.1–360 MeV/amu) and ion species (⁴He ...²³⁸U). Excellent results with respect to energy resolution, Δ E/E ranging from 1 to 5 × 10^–3 even for the heaviest ions, and other basic detector properties such as energy linearity with no indication of a pulse height defect, energy threshold, detection efficiency and radiation hardness have been obtained, representing a considerable improvement as compared to conventional heavy ion detectors based on ionization. With the achieved performance, calorimetric low temperature detectors bear a large potential for applications in various fields of basic and applied heavy ion research. A brief overview of a few prominent examples, such as high resolution nuclear spectroscopy, high resolution nuclear mass determination, which may be favourably used for identification of superheavy elements or in direct reaction experiments with radioactive beams, as well as background discrimination in accelerator mass spectrometry, is given, and first results are presented. For instance, the use of cryogenic detectors allowed to improve the sensitivity in trace analysis of ²³⁶U by one order of magnitude and to determine the up to date smallest isotope ratio of ²³⁶U/²³⁸U = 6.1 × 10^–12 in a sample of natural uranium.

Besides the detection of heavy ions, the concept of cryogenic detectors also provides considerable advantage for X-ray spectroscopy in atomic physics with highly charged heavy ions. Such detectors are to be used in near future for sensitive tests of quantum electrodynamics in very strong electromagnetic fields by a precise determination of the 1s Lamb shift in hydrogen-like heavy ions. The status of development of a high-resolution, and highly efficient detector for hard X-rays is reported, the performance of which is with Δ E/E = 1.1 × 10^–3 for E _γ = 60 keV close to fulfill the demands of the Lamb shift experiment.