The ATLAS detector has been built to study the reactions produced by the Large Hadron Collider (LHC). ATLAS includes a system of liquid argon calorimeters for energy measurements. The electronics for amplifying, shaping, sampling, pipelining, and digitizing the calorimeter signals is implemented on a set of front-end electronic boards. The front-end boards are installed in crates mounted between the calorimeters, where they will be subjected to significant levels of radiation during LHC operation. As a result, all components used on the front-end boards had to be subjected to an extensive set of radiation qualification tests. This paper describes radiationtolerant designs, radiation testing, and radiation qualification of the front-end readout system for the ATLAS liquid argon calorimeters.

Nearly twenty years ago Ya. B. Zeldovich pointed out that free neutrons, if sufficiently slow, could in principle be stored in a closed “bottle”—presumably for periods up to the beta decay lifetime, about 103 seconds. Apparently, according to Bruno Pontecorvo, Enrico Fermi had mentioned this possibility as early as the middle 1930's, but Zeldovich's paper was the first published discussion. The basis for the belief that neutrons could be stored in this way was the behavior of the effective potential for the interaction of neutrons with matter, which for many substances becomes repulsive when the neutrons are sufficiently slow. Thus there is a strong suppression of inelastic processes for these very slow neutrons (energies below about 10−7 eV), and they are totally reflected upon collisions with, for example, container walls.

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A new type of per-fluorinated polymer, “Low Temperature Fomblin,” has been tested as a wall coating in an ultracold neutron (UCN) storage experiment using a gravitational storage system. The data show a UCN reflection loss coefficient η as low as ≈ 5 × 10−6 in the temperature range 105 K to 150 K. We plan to use this oil in a new type of neutron lifetime measurement, where a bellows system (“accordion”) enables to vary the trap size in a wide range while the total surface area and distribution of surface area over height remain constant. These unique characteristics, in combination with application of the scaling technique developed by W. Mampe et al. in 1989, ensure exact linearity for the extrapolation from inverse storage lifetimes to the inverse neutron lifetime. Linearity holds for any energy dependence of loss coefficient µ(E). Using the UCN source at the Institut Laue Langevin we expect to achieve a lifetime precision below ±1 s.

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