A multi-purpose particle detector for measurement of decays of highly-charged ions in storage rings

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The measurement of decay properties of ions orbiting in a storage ring is a complementary path to conventional measurement techniques. It has been proven to be a very successful tool for the simultaneous mass measurement of dozens of ions injected in the storage ring. Also exotic decay modes of ions with only a few or no electrons, so-called "highly-charged ions" (HCI) have been discovered and measured for the first time in storage rings. Examples are the "bound-state beta decay" that leads to an acceleration of the decay of some nuclei in the fully ionized state, e.g. 187Re(75+) decayed 1 billion times faster than in the neutral state, and stable neutral 163Dy becomes radioactive and decays with a half-life of 45 days when transferred into the fully-ionized 66+ charge state. It is a modern nuclear physicists dream to be able to "manipulate" how fast material can decay. Nuclear transmutation, the transformation of long-lived radioactive waste into something that decays faster, could greatly benefit from these studies- however the strong acceleration of decay modes has so far only been observed for a few cases that are not the main contributors of radioactive waste. For the measurements in the storage rings two types of detectors are needed: one for the destruction-free detection and identification of the ions while they orbit in the storage ring, and one detector for the detection of the decay products if they cannot be stored in the storage ring due to its limited momentum acceptance. For the destruction-free identification of the ions and respective mass measurement a device called "Schottky pickups" is used. For the detection of decay products that leave the acceptance of the ring particle detector telecopes are used. The foundation for this proposal has been laid by my Helmholtz Young Investigators Research Group in 2010-15. In collaboration with the TU Munich my group has constructed the prototype detector "CsISiPHOS" (CsI-Silicon Particle detector for Heavy ions Orbiting in Storage rings) and tested and commissioned it with beam in 2015. CsISiPHOS is a multi-purpose detector that has been built to detect various particles emitted in decay processes in the Experimental Storage Ring (ESR) and/or Collector Ring (CR) and is an integral part of the ILIMA (Investigation of LIfetimes and MAsses) program at FAIR. The detector has to provide a position resolution corresonding to the beam diameter in the ring after cooling, as well as unique particle identification in mass A and nuclear charge Z to allow a clear separation of isobaric contaminants. Several improvements have been suggested for the upgraded version of this detector which have been described in the TDR that has been submitted to the FAIR ECE council in 2017/18. If funded, this new detector and the new data aquisition system will be used in upcoming FAIR Phase-0 experiments starting in summer 2021.