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


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