Note: Page still in progress -Alex
Table of Contents
XTCAV SIMS
This summer I ran simulations of the XTCAVF component of the facet-II accelerator
- The purpose was to simulate the process to measure longitudinal quantites about the beam
- TCAV stands for 'Transverse deflecting CAVity'
- These simulations used the bmad + tao interface in python
- The simulations began at the component BEGBC20 (beginning of bunch compressor 20)
- The input beam files were generated from jitter studies performed by fellow intern Robin Hwang
- I was able to vary both the deflection angle and XTCAV voltage to observe the results
Simulations with the XTCAV turned off:
Transverse Phase Space Longitudinal Phase Space
Transverse Phase Spaces with the XTCAV Turned On:
6 MV TCAV Voltage 10 MV TCAV Voltage
14 MV TCAV Voltage 18 MV TCAV Voltage
- One can observe the output transverse phase spaces resembling the original longitudinal phase space more and more as the voltage is increased
Analysis Methods
- The main point of these simulations was to reconstruct longitudinal aspects of the beam, most importantly the bunch length
- The bunch length measurement requires the acquisition of a value known as the streak parameter
- This parameter is obtained by performing a calibration on the XTCAV
- The calibration involves varying the deflection angle PHI and measuring the resulting centroid in the dimension of deflection (in my case, x)
- This is because the centroid recieves a small kick in some direction when the TCAV angle is not perfectly 90 degrees
- The relationship between bunch width and angle is sinusoidal, but at small angles this can be approximated as linear
- The streak parameter is the slope of this linear fit
- Using the streak parameter we can reconstruct the longitudinal bunch length, often denoted sigma z
- The output sigma x (bunch width) of the TCAV is related to the voltage of the TCAV quadratically
- The coefficient of the quadratic term in this relationship is a function of the original sigma z
- To find the original sigma z, find the relationship between sigma x and TCAV voltage by fitting a voltage scan to a parabola
Calibration Process:
Linear fit of the centroid vs. angle Sinusoidal fit of centroid vs. angle
Reconstructing Sigma Z:
Parabolic fit of the bunch width vs. TCAV voltage