Low-energy heating of ultracold neutrons during their storage in material bottles

We have studied the low-energy heating of ultracold neutrons during their storage. On fomblin, it is greatly suppressed for the low temperature liquid and at solidification. For non-magnetic solid materials, upper limits of 5 x 10(-9) (Be) and 3.6 x 10(-8) (Cu) per collision were found. Therefore, low-energy heating is not the reason for anomalous losses of (2-3) x 10(-5) per collision on beryllium surfaces. (C) 2003 Elsevier Science B.V. All rights reserved.