Module Flipper_gradient

# VITESS Module Flipper_gradient

This module simulates spin precessions in the magnetic field of special kind. The first part of such field is a rotating magnetic field. Amplitude of this field must be changing by sinus distribution with semi-period, which is equal of the appropriate dimensions of the rotating field volume. Magnetic field can be rotated around the axises OX or OY or OZ. The axis OX has the direction of neutron flight. Permanent value of amplitude can be given also.
The second part of general field is a guide magnetic field.
The spin precessions are treated classically i.e. this module only rotates the spin vectors belonging to trajectories which pass through the rectangular geometry.
The random magnetic field can be added also.
No attenuation is considered during the flight.
-----------FIRST-PART-----------ROTATING FIELD----------------------
FORMULAS OF ROTATION: AROUND AXIS 0X
X = X0
Y = Y0 + FieldValue*sin(Omega*(T + TOF) + BeginPhase)
Z = Z0 + FieldValue*cos(Omega*(T + TOF) + BeginPhase)
FORMULAS OF ROTATION: AROUND AXIS 0Y
X = X0 + FieldValue*sin(Omega*(T + TOF) + BeginPhase)
Y = Y0
Z = Z0 + FieldValue*cos(Omega*(T + TOF) + BeginPhase)
FORMULAS OF ROTATION: AROUND AXIS 0Z
X = X0 + FieldValue*cos(Omega*(T + TOF) + BeginPhase)
Y = Y0 + FieldValue*sin(Omega*(T + TOF) + BeginPhase)
Z = Z0
X0, Y0, Z0 - components of guide magnetic field [Oe=Gauss],
Omega = 2*PI*omega/1000, omega = [Hz], Omega = [rad/ms],
FieldValue - Strength (Amplitude) of rotating magnetic field in Oe=Gauss,
BeginPhase in degree
TOF - time of flight of neutron from preceding modules for rotating field phase.
So, if TOF=0 is used: The magnetic field is directed vertically upwards for rotating around of the axis 0X, when NEUTRON WAS LEFT THE MODERATOR SURFACE.
Also, if TOF is zero, the rotation of magnetic field and neutron time of flight are NOT SYNHRONIZED and so unsuatible for Spin Echo simulations!!!
The amplitude FieldValue can have a 3 types of distributions:
1. sinus law (with semi-period - appropriate dimensions of the magnetic field volume)
2. permanent law
3. solinoid formula (not yet active)
-----------SECOND-----PART: GUIDE-MAGNETIC-FIELD---
This part can have a 3 types of distribution too:
1. cosine law : with semi-period - appropriate dimensions of the magnetic field volume
2. linear law : with period - appropriate dimensions of the rotating field volume
3. pernanent law
We have simulated a gradient flipper with such distributions:
rotating magnetic field: sinus law
guide magnetic field: linear law
and have got a good results.
The frequency of rotating and components of guide magnetic fields can be randomized.

### Module parameters

Parameter Unit | Description | Command option
dimensions of field volume X,Y,Z [cm] | X, Y, Z Dimensions of the flipper | -X, -Y, -V
position main X,Y,Z [cm] | Center position of the flipper. | -k, -l, -m
offset horiz. [deg] | Horizontal (around vertical axis) rotation angle of the magnetic field volume. | -i
output X,Y,Z [cm] | Position of the output frame (in the input frame). | -p, -r, -s
Number of domains in the X direction | Number of domains in the X direction (flight direction) | -C
Number of domains in the Y direction | Number of domains in the Y direction | -D
Number of domains in the Z direction | Number of domains in the Z direction | -E
Rotating field around given axis | Choose rotating field around of a axis OX or OY or OZ , values 0, 1, 2 respective | -M
Strength of rotating magnetic field [Oe=gauss] | Strength(Amplitude) of the rotating magnetic field. | -d
Frequency of rotating [Hz] | Rotation frequency of the magnetic field. | -w
Begin Phase [degree] | Initial phase for the rotating field. | -z
Law of amplitude changing | Amplitude of the rotating magnetic field is changing by sinus (with semi-period - appropriate dimensions of rotating field volume) law, permanently and by solinoid formula (not yet active) | -h
Deviation of amplitude [%] | Deviation of amplitude of the rotating magnetic field in percent | -a
Axis of amplitude changing | Key-Direction for changing of amplitude of the rotating field along given axis OX, OY or OZ, values 0,1,2. Actually, if amplitude changing by sinus was chosen | -y
Amplitude distribution | Distribution of random values: amplitude of the rotating magnetic field {Normal Uniform} {0 1} | -e
Deviation of frequency [%] | Deviation of Rotation frequency of the magnetic field in percent | -b
Frequency distribution | Distribution of random values: frequency of the rotating magnetic field {Normal Uniform} {0 1} | -v
TOF from preceding modules | Value 1 - use the neutron TOF from preceding modules for rotating field phase; 0 - No -> TOF = 0; | -n
Law of changingof the guide magnetic field | Laws of distribution of guide magnetic field: cosine law (with semi-period - appropriate dimensions of rotating field volume), linearly and pernanently | -u
Amplitude changing along axis | Key-Direction for amplitude changing of guide field along given axis OX, OY or OZ, values 0,1,2. Actually, if cosinus law of changing was given | -t
Permanent or initial component X, Y and Z [Oe] | Permanent(for cosine amd permanent laws) or initial(for linear law) value of the X, Y or Z components (projection in the axis 0X, OY, OZ) of the guide magnetic field, Oe=Gauss | -I, -A, -K
Amplitude or final component X, Y and Z [Oe] | Amplitude(for cosine law) or final(for linear law) value of the X,Y,Z component (projection in the axis 0X, OY, OZ) of the guide magnetic field, Oe=Gauss | -P -Q -R
Additional random\n magnetic field [Oe] | Amplitude of additional random magnetic field | -q
Output results | Output intermediately results of simulations(spin and total magnetic field during flight) in the file {yes no} {1 0} | -S
Output file: polarisation | Name of file for: results - polarisation, spin components | -O
Output file: magneticfield | Name of file for output results - total magnetic field components | -N

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Last modified: Sep 30 19:07:01 MEST 2003