The `Vertical_Bender` Component

Multi-channel bender curving vertically down.

Identification

• Author: Andrew Jackson, Richard Heenan
• Origin: ESS
• Date: August 2016, June 2017
• Version: \$Revision\$

Description

```Based on Pol_bender written by Peter Christiansen
Models a rectangular curved guide with entrance on Z axis.
Entrance is on the X-Y plane. Draws a correct depiction of
the guide with multiple channels - i.e. following components need to be
displaced.
Guide can contain multiple channels using horizontal blades
Reflectivity modeled using StdReflecFunc and {R0, Qc, alpha, m, W} can be set
for top (outside of curve), bottom (inside of curve) and sides
(both sides equal), blades reflectivities match top and bottom (each channel is
like a "mini guide").
Neutrons are tracked, with gravity, inside the wall of a cylinder using distance
steps of diststep1. Upon crossing the inner or outer wall, the final step is
repeated using steps of diststep2, thus checking more
closely for the first crossing of either wall. If diststep1 is too
large than a "grazing incidence reflection" may be missed altogether.
If diststep1 is too small, then the code will run slower!
Exact intersection tmes with the flat sides and ends of the bender channel are calculated
first in order to limit the time spent tracking curved trajectories.
Turning gravity off will not make this run any faster, as the same method is used.

28/06/2017 still need validation against other codes (e.g. for gravity off case)

Example:
Vertical_Bender(xwidth = 0.05, yheight = 0.05, length = 3.0,
radius = 70.0, nslit = 5, d=0.0005, diststep1=0.020, diststep2=0.002,
rTopPar={0.99, 0.219, 6.07, 3.0, 0.003},
rBottomPar={0.99, 0.219, 6.07, 2.0, 0.003},
rSidesPar={0.99, 0.219, 6.07, 2.0, 0.003},

See example instrument Test_Vert_Bender

%BUGS
Original code did not work with rotation about axes and gravity.
This tedious tracking method should work (28/6/17 still under test) for a vertical bender, with optional
rotation about x axis and gravity (and likely rotation about y axis but needs testing,
and even perhaps rotation about z axis as in rotated local frame Gx then is non zero but the edge solver still works).
Would also need test the drawing in trace mode).

GRAVITY : Yes, when component is not rotated

```
WARNING: This is a contributed Component.

Input parameters

Parameters in boldface are required; the others are optional.
Name Unit Description Default
rTopPar - Parameters for reflectivity of bender top surface {0.99
rBottomPar - Parameters for reflectivity of bender bottom surface {0.99
rSidesPar - Parameters for reflectivity of bender sides surface {0.99
xwidth m Width at the guide entry
yheight m Height at the guide entry
length m length of guide along center
radius m Radius of curvature of the guide (+:curve up/-:curve down)
G 9.8
nchan 1 Number of channels 1
d m Width of spacers (subdividing absorbing walls) 0.0
debug - 0 to 10 for zero to maximum print out - reduce number of neutrons to run ! 0
endFlat 1 If endflat>0 then entrance and exit planes are parallel. 0
drawOption 1
alwaystrack - default 0, 1 to force tracking even when gravity is off 0
diststep1 0.020 m inital collision search steps for trajectory in cylinder when gravity is non zero 0.020
diststep2 0.002 m final steps for trajectory in cylinder 0.002

Output parameters

Name Unit Description Default
localG
normSides
normIn
normOut
pointTop
pointBot
pointIn
pointOut
rTopParPtr
rBotParPtr
rLeftParPtr
rRightParPtr
i_bounce