Changing Media

The following can be done:-

• Modify word KGEDS_IDM of the GEDS bank to change the physical media code (as defined in the MEDA bank). For example, suppose the D$_2$O region is to be filled with H$_2$O , proceed as follows:-
  1. Look at the geometry summary printout that appears as part of the initialisation output. From this you will see that region types 100 and 212 contain D$_2$O . Note: for a complete list of region types see:-

     ..snoman/n_nn/code/id_regions.inc

     Companion/Id Codes/Regions

  2. Also from this summary you can see that the physical media code for H$_2$O is 100. Note: for a complete list of physical media codes see the MEDA 1 titles bank.

  3. Change the KGEDS_IDM word of the GEDS banks 100 and 212 to the new media code 100. This can be done with the commands:-

     set bank GEDS 100 word 3 to 100
     set bank GEDS 212 word 3 to 100

     although it is better to use the symbolic commands:-

     $geom_media $D2O $light_water
     $geom_media $ACRC_IVL $light_water

  If changing both D$_2$O and H$_2$O to air for an air fill simulation (see the command file air_fill.cmd), SNOMAN automatically switches to the correct PMT bank, which describes the angular response of the PMT, to take account of this change. Also the time fitter compensates for the change in the velocity of light.

• Change or add new entries to the MEDA to change the optical properties of the media available to SNOMAN. Note that dividing the physical media code by 100 gives the generic media code for which there has to be an entry in the PEGS data file. For more information see:-

  Companion/Id Codes/Regions and Media Codes

• To change the atomic properties of any media requires an update to the PEGS file which is beyond the scope of this manual!