The neutron beam shutters/absorber - up to July 2013

(latest version⁽¹⁾)

Two different shutters/absorbers are installed in the nELBE setup, one at each end of the neutron collimator, i.e. one in room 123, where the liquid Pb loop is placed, and one in the experimental cave room 111c.

The shutter in room 111c consists of a tungsten cylinder (length = 26 cm, diameter = 18 cm) and is used to close the collimator.

The shutter/absorber in room 123 is used for two purposes: At first it can debar all neutrons and gammas from entering the collimator, and second it gives the possibility to mount different absorbers to manipulate the neutron and gamma spectrum or to perform transmission experiments.

The layout of the neutron beam shutter/absorber is shown in the drawing below. A tungsten cylinder is used as beam shutter. 4 holders can be used for mounting several absorbers. The whole apparatus can be moved by remote control using the ELBE WinCC⁽²⁾ to position the absorber of choice in front of the collimator.

At the moment the configuration is as follows:

position	material	length	diameter
1	W	150 mm	140 mm
2	Pb (#4)	30 mm	25 mm
3	Pb (#5) + Fe	30 + 20 mm	25 / 25 mm
4	Pb (#6) + Au	30 + 16 mm	25 / 26 mm
5	PE	300 mm	60 mm

The following absorbers are available:

material	length	diameter	mass
Al	40.0 mm	60.0 mm
Au	16.0 mm	26.0 mm	163.76 g
C	30.0 mm	25.0 mm	24.6746 g
Fe	20.0 mm	25.0 mm	77.2740
Pb	30.0 mm	25.1 mm
Pb (#4)	30.0 mm	25.0 mm	161.71 g
Pb (#5)	30.0 mm	25.0 mm	161.74 g
Pb (#6)	30.0 mm	25.0 mm	161.71 g
Pb	59.0 mm	25.0 mm	318.3 g
Pb	98.0 mm	25.0 mm	529.2 g
PE	10.0 mm	60.0 mm	26.7615 g
PE	50.0 mm	60.0 mm	134.6058 g
PE	300.0 mm	60.0 mm
Ta	15.0 mm	25.1 mm	124.0 g
Ta	25.5 mm	25.1 mm	210.0 g
Ta	35.2 mm	25.1 mm	290.1 g