Abstract: A cryostat configuration for keeping liquid helium comprising an outer jacket (3) surrounding a helium container (1) connected at at least two suspension tubes (2) to the outer jacket (3), wherein the helium container (1) also comprises a neck tube (5) whose upper warm end is connected to the outer jacket (3) and whose lower cold end is connected to the helium container (1) and into which a multi-stage cold head (6) of a cryocooler is installed, wherein the outer jacket (3), the helium container (1), the suspension tubes (2) and the neck tube (5) delimit an evacuated space (7), and the helium container (1) is surrounded by at least one radiation shield (4) which is connected in a heat-conducting fashion to the suspension tubes (2) and also to the neck tube (5) of the helium container (1) is characterized in that there is a direct connection (8) between the warm ends of the suspension tubes (2) and the neck tube (5) through which helium gas can flow.

Abstract: A magnet system with a magnet arrangement (M), a working volume (V) and a pulse tube cooler (P) with magnetic regenerator material (r) is characterized in that a shielding (m) of magnetic material is provided which reduces the stray field of the magnet arrangement at the location of the magnetic regenerator material (r) and is characterized in that 1 3 ? ? m ~ Reg ? R ? + ? m Mag ? ? ? ? ? x ? < 1 6 ? ? m Reg ? R ? , wherein mMag is the dipole moment of the magnetic material of the shielding (m), ?? is the vibration amplitude of the magnetic material of the shielding (m), mReg is the amplitude of the dipole fluctuations of the magnetic regenerator material (r) in one cycle without magnetic shielding (m), {tilde over (m)}Reg is the amplitude of the dipole fluctuations of the magnetic regenerator material (r) in one cycle with magnetic shielding (m), and R is the average separation of the magnetic regenerator material (r) from the working volume (V).

Abstract: The invention relates to a material for electric contacts taking silver tin-oxide as basis, consisting of silver or mainly silver-containing alloy, tin oxide and other oxides or carbides of tungsten, molybdenum, vanadium, bismuth, titanium, and/or copper.