Numerical integration of Bethe formula in Excel: help!


by Moho
Tags: alpha, bethe, bloch, integration
Moho
Moho is offline
#1
Feb21-13, 09:40 AM
P: 2
Hello,

I am a PhD student in geology in need of help from a physicist! Can somebody spot the mistake in my spreadsheet?

I am using an Excel spreadsheet (attached .xls) to integrate the Bethe formula in order to estimate the range (in cm) of alpha particles in quartz. I am using the version of the formula given in Groom and Klein's "Passage of Particles through Matter": http://pdg.lbl.gov/2009/reviews/rpp2...les-matter.pdf (but ignoring the density effect correction because I am not interested in high energies).

In Excel, I can plot the Bragg peak (dE/dX against x) or the energy of the alpha particle (E against x). Something is very wrong: the Bragg curve just goes up and up and never comes down again (don't be misled by Excel plotting #NUM! as 0). I would expect dE/dX to start out at something like 500 and then smoothly increase up to the peak (like the Bragg peaks in Google image search).

I must be doing something right, though, because it looks as if the stopping distance is going to be close to what I would expect (about 0.04 cm).

Can anybody find the problem in the attached spreadsheet? Reward: credit in my thesis acknowledgements!

Many thanks!

Moho
Attached Files
File Type: zip BETHEVERSION3.zip (289.9 KB, 5 views)
Phys.Org News Partner Physics news on Phys.org
Physicists design quantum switches which can be activated by single photons
'Dressed' laser aimed at clouds may be key to inducing rain, lightning
Higher-order nonlinear optical processes observed using the SACLA X-ray free-electron laser
mfb
mfb is offline
#2
Feb21-13, 02:57 PM
Mentor
P: 10,836
For low energy (βγ<0.03), the Bethe-Bloch formula gives wrong results, as shown in figure 27.1 in the pdf.
Apart from that: After the energy is 0, the energy loss should be 0 as well, giving a nice Bragg peak.


Register to reply

Related Discussions
Bethe-formula VS SRIM for Uran in Polycarbonate High Energy, Nuclear, Particle Physics 0
Bethe-Bloch formula for muons High Energy, Nuclear, Particle Physics 0
Bethe Bloch formula High Energy, Nuclear, Particle Physics 1
obtaining range from bethe-bloch formula High Energy, Nuclear, Particle Physics 2
Bethe formula question High Energy, Nuclear, Particle Physics 3