The neutron beam shutters/absorber - up to May 2014
Two different shutters/absorbers are installed in the nELBE setup, one at each end of the neutron collimator, i.e. one in room 111b, where the liquid Pb loop is placed, and one in the experimental cave room 125.
The shutter in room 125 consists of a tungsten cylinder (length = 26 cm, diameter = 18 cm) and is used to close the collimator.
The absorber ladder in room 111b 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 absorber ladder is shown in Fig. 1. A tungsten cylinder is used as beam shutter. 4 absober holders can be used for mounting several absorbers. The whole apparatus can be moved by remote control to position the absorber of choice in front of the collimator.
Fig. 1 Technical drawing of the absorber ladder
At the moment the configuration is as follows:
The following absorbers are available:
|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) (+Sb)||30.0 mm||25.0 mm||161.71 g|
|Pb (#5) (+Sb)||30.0 mm||25.0 mm||161.74 g|
|Pb (#6) (+Sb)||30.0 mm||25.0 mm||161.71 g|
|Pb (#7) (pure)||30.0 mm||25.0 mm||167.0309 g|
|Pb (#8) (pure)||30.0 mm||25.0 mm||166.9559 g|
|Pb (#9) (pure)||30.0 mm||25.0 mm||167.0020 g|
|Pb (#10) (pure)||30.0 mm||25.0 mm||167.2083 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|
|U-238 (99.9 %)||5.81 mm||50.88 mm||224 g|
|U-238 (99.9 %)||5.75 mm||50.88 mm||224 g|
|W (#2)||15.92(3) mm||25.3 mm||153.2001 g|
To change from one absorber position to another the following numbers of seconds is needed: