LaserComptonScat

Notes on Syed's GEANT4 project for Laser Compton Scattering at the IAC

2/7/08

Step 1: Configure Event generator in which electron parameters can be changes. Move the source left and right of the center. Change is momentum direction; going left and going right.

Step 2: comment out electron and add gamma. get it to move in the same way.

Step 3: turn them both on

Step 4: if fail then find references on event Generator with 2 intersecting beams, perhaps ILC, LHC or BaBar has one.

2/14/08

Problem last week was due to editing the wrong file.

We now have a event generator which starts an electron and a photon moving toward eachother.

We see and event when the photon energy is 500 keV and only the compton process is turned on.

Next step:

1.) edit the Stepping Verbose so only a Compton event is printed out

2.) add an event counter so we know how many beam triggers are done to get the event( edit SteppingVerbose.h, add a global variable to the class definition)

output : event number, Photon position, Electron position, Photon and Electron initial and final momentum.

3.) Compare output with BDSIM at 500 keV

4.) Insert new physics process for Low Energy Compton

2/28/08

1.) edit the Stepping Verbose so only a Compton event is printed out (done)

2.) add an event counter so we know how many beam triggers are done to get the event( edit SteppingVerbose.h, add a global variable to the class definition)

output : event number, Photon position, Electron position, Photon and Electron initial and final momentum.

3.) Compare output with BDSIM at 500 keV

4.) Insert new physics process for Low Energy Compton (done)

Still need to do 2 &3.

Compare hand calculation of an event or two with GEANT4 output

3/6/08

Goals for last week

1.) Compare hand calculation of an event or two with GEANT4 output

2.) add an event counter so we know how many beam triggers are done to get the event( edit SteppingVerbose.h, add a global variable to the class definition)

output : event number, Photon position, Electron position, Photon and Electron initial and final momentum.

3.) Compare output with BDSIM at 500 keV (BDSIM crashes at this high energy)

Tasks for next week:

1.) How many GEANT4 triggers does it take to get an event when E-gamma = 30 eV

Zero/10^7. However, if I set the E-gamma=300 eV then I see 1819 triggers out of 10 million iterations.

2.) remove detector which blocks reactions for 0<Z<200

   [box]Commented out Sensitive Detector function in DetectorConstruction.cc. I still see the SD in display[/box]

3.) Store tracking info for photon and electron into variables for printing out

   [box]Show the text file for 300 eV laser and 20 MeV electron[/box]

4.) Compare BDSIM and GEANT4 for E-gamma = 300 or 30 eV

   [box]BDSIM crashes at 300 eV[/box]

5.) Any measured X-sections for 2 eV Compton?

   [box]Was not able to find on internet. BDSIM however, uses GEANT4 database...We might need to dig into their code, I got the source code[/box]

3/13/08

Tasks:

1.) fix output file so electons and photon from same event on same line

  o Geant4 output.txt:

Variable	value
# Triggers	153610
Compton Event #	1
Scattered Photon energy (keV)	0.299784
photon X position	0
photon Y position	0
photon Z position	-441.431
photon X Momentum	6.30938e-05
photon Y Momentum	0.000285127
photon Z Momentum	-6.77687e-05
Particle ID	22
Scattered e- KE (keV)	0.000215785
Scattered electron X position	-177.027
Scattered electron Y position	-800
Scattered electron Z position	590.444
Scattered electron X Momentum	-6.30938e-05
Scattered electron Y Momentum	-0.000285127
Scattered electron Z Momentum	0.000367769
Particle ID	11

[math]\lambda^{\prime} = \lambda + \lambda_C (1-\cos(\theta)) = \frac{2 \pi}{\omega^{\prime}} = \frac{ch}{E_{\gamma}^{\prime}} = \frac{12,400 \mbox{Angstroms}}{E_{\gamma}^{\prime}}[/math]

[math]\lambda_C[/math] = electron compton wavelength = [math]\frac{h}{m_ec} = 2.43 \times 10^{-12} m[/math]

[math]E_k = \hbar \omega \frac{\lambda_C}{\lambda} \frac{1- \cos(\theta)}{1 + \frac{\lambda_C}{\lambda} \left (1 - \cos(\theta) \right )}[/math] = electron final kinetic energy

[math]\phi = \cot \left [ \left ( 1+ \frac{\lambda_C}{\lambda}\right ) tan(\frac{\theta}{2}\right ][/math] = ejected electron angle w.r.t original photon direction

     15361 ||   1   || 0.299784   0   0   -441.431   6.30938e-05   0.000285127   -6.77687e-05   22   0.000215785   -177.027   -800   590.444   -6.30938e-05 -0.000285127   0.000367769   11   
    32685.8   2   0.299791   0   0   -131.765   -7.34024e-05   0.000285186   -5.61732e-05   22   0.000208981   192.024   -746.061   800   7.34024e-05   -0.000285186   0.000356173   11   
    33535.9   3   0.299682   0   0   -754.315   -0.000175966   -1.63899e-05   -0.000242026   22   0.000318029   504.599   46.9997   800   0.000175966   1.63899e-05   0.000542026   11   
      34157   4   0.299864   0   0   -579.415   -7.39129e-05   -0.000282637   6.7614e-05   22   0.00013635   209.21   800   78.3512   7.39129e-05   0.000282637   0.000232386   11   

. . . .

2.)Compare compton scattering between BDSIM and GEANT4 for 300 eV photon incident on a 20 MeV electron

BDSIM	GEANT4

o BDSIM (5,000,000 Iterations):

o Geant4 (5,000,000 iterations):

3.) remove physics processes and run 10^9 events piece mealed so you save event generator seed every 10^8

o Still waiting for run_0.rndm, run_1.rndm...., files on inca. Process at the moment is executing!