RF background generator in G4MICE

Video conference 17/12 -03

Yagmur Torun

Rikard Sandström

Geneva University

Options

There are several options available to the user to generate the RF background. Please see Yagmur's talk 3 Dec.Some of these are

•FixedThe user specifies a constant energy for the background electrons/photons.

•FlatFlat energy distribution

•User •G4MICE reads the spectrum from histogram files (ordinary text format).•Here the user can specify whether the entries should be interpreted as discrete, or flat (centered at that energy). In the latter case the bins must be equidistant.

Discrete spectrumExample of discrete spectrum (User)

This spectrum was created by moving the RF background source inside the upstream TPG in order to avoid material effects.

The option is User with energies 2, 4, 6, 8 MeV, each with a weight.

The electrons initially from the background emitter are automatically painted red (emigrants) since the have high enough energy to escape the detector.

Some high energy electrons reach the downstream TPG, and are thus green (vagabonds).

RF electrons

Continous spectrumExample of continous spectrum

This spectrum was created in a very similar way as in the previous slide.

Energy steps

High energy hits on the other detector (no cooling)

Discrete photon spectrum

Continous photon spectrum

New simulation

• Tracking now fixed, allowing low energy electrons to propagate correctly in fields.

• Bug in full simulation mode prevents using electrons onto absorbers right now, however:

• With 3000 MHz of RF electrons (proposal), 50 microsec open gate and previous similated photons/e = 3.54% you get 5310 gamma per open gate.

• This is used in DetectorsOnly mode shooting (all) onto the upstream TPG.

• Only one muon per open gate (no pileup)

No background, 100 mu

Almost all electrons are confined (98%)

Most photons from entrance face

Some photons from sides

Reproducing old spectrum...

From pr

esen

tation

24 se

pt -0

3

Photon energy

Should look like previous spectrum

Shooting photons on the upstream TPG

Specified 531000%

Backscattered from GEMs & Hexaboard

Range of photons

All photons go through face to face

Electron energy

165 electrons per open gate, 5 of these from muon

Upstream TPG

Downstream TPG

Range of electrons

Upstream direction

Downstreamdirection

Many e's travel perpendicular to beam axis

Conclusion• RF background simulation works and does not

contradict previous results.

• With no background we had a ratio e/open gate = 4.78.

• With the given assumptions, this number is 164.53 in the TPG with RF photon background turned on.

• About one tenth of them go through the detector face to face.

– Previously (24 Sept) I said 10-20 go through face to face.

• Many of the electrons enter and leave with a very large angle wrt beamline.

Future plans

• Should use electrons on absorbers ASAP.

• Higher statistics needed (when bug fixed).

• Use background generator in SciFi Recon and Analysis with MICE2ROOT and compare with no background (possible now).

• Late spring, should be able to do the same for TPG (Olena).

God Jul!