#!/usr/local/bin/perl5
# This script is made to remove the remanent magnetic field from the dipole magnet at  the `PITZ` 
# by S.v.Coelln , made during the summerstudentprogramm 2002 at the DESY Zeuthen
# modified by Bert Schoeneich, 20.12.2007, 10:30 for CTS.DIPOLE
# values for CTS at 14.01.2008 from Juliane Roensch

# [PART 1] - list of params

$T=15 ; # time of one periode in seconds
$min=0.005 ; # value when the mainloops ends (Ampere)
$startcurrent=3.0 ; # current which to start with (Ampere)
$invdamp=25 ;  # inverse damp factor for the exp-function (increasing this results in decreasing damp) 

$pi=3.1413 ;

# [PART 2] - Calculation of the whole time which is needed to process the script
$zeit=-$invdamp*log($min/$startcurrent) ;
print "Processing time:".(int($zeit)+5).`\n` ; # 5 seconds of sleep plus 1 sec for rounding integer = 6

$testcurrent=$startcurrent ;

# [PART 3] - setting the startcurrents for the Dipole 
system "doocsput -c PITZ.CA/MAGNETS/CTS.DIPOLE/SETPOINT -t 2 -d $startcurrent" ; # set the current for the dipole
system "sleep 3" ; # give time for reaching stationary state


# [PART 4] - the main loop 
for($i=0 ; $testcurrent>$min ; $i++)
      {
	$testcurrent=$startcurrent*exp(-$i/$invdamp) ; #just the damped term which is used for aborting loop
	$current=$testcurrent*cos(2*$pi*$i/$T); # values of the damped cosine oszilation
        system "doocsput -c PITZ.CA/MAGNETS/CTS.DIPOLE/SETPOINT -t 2 -d $current" ; 
        system "sleep 1" ;
      }

# [PART 5] - decrease the current to the minus ten"th of the last value 
$endcurrent=-0.5*($current) ;
system "doocsput -c PITZ.CA/MAGNETS/CTS.DIPOLE/SETPOINT -t 2 -d $endcurrent" ;
system "sleep 1" ;

#  Set current to zero
system "doocsput -c PITZ.CA/MAGNETS/CTS.DIPOLE/SETPOINT -t 2 -d 0" ;