Beam PID

last modified: 2024-01-22 by Kodai Okawa

In the F2 focal plane, we check the secondary beam condition. In other words, identify the beam particles we want and adjust the beamline parameters to get the most amount of the beam particle. Therefore, we need to identify the beam ion from the data. To do so, we perform simulation.

This is almost the same with this web application. This web application uses enewz energy loss calculation, but PID using artemis uses SRIM.

These are the source code for the PID calculation.

Principles

The simple principle of PID (Particle IDentification) is described.

First, the energies of the various beam ions are determined from the value of the magnetic rigidity ( $B\rho$) of the dipole magnets. The values are then calculated using relativity.

$$ m_0\gamma\frac{v^2}{\rho} = qevB $$ $$ B\rho = \frac{m_0\gamma\beta c}{qe} $$ $$ \frac{B\rho qe}{c} = m_0\frac{\beta}{\sqrt{1-\beta^2}} $$

From this equation, solving for $\beta^2$,

$$ \beta^2 = \frac{1}{1+\left( \frac{m_0 c}{B\rho qe} \right)^2} $$ $$ \frac{1}{\sqrt{1-\beta^2}} = \sqrt{1+\left( \frac{B\rho qe}{m_0 c} \right)^2} $$

Relativistic energy $E$ is

$$ E = \frac{m_0 c^2}{\sqrt{1-\beta^2}} $$ $$ E^2 = \left(m_0 c^2\right)^2 + \left( B\rho qec \right)^2 $$

Therefore, from this equation, $E$ can be obtained from $B\rho$ and the kinetic energy can be derived from the following relationship.

$$ E = E_{kin} + m_0 c^2 $$ $$ E_{kin} = m_0 c^2\left( \sqrt{1+\left( \frac{B\rho qec}{m_0 c^2} \right)^2} -1 \right) $$

The equation for determining velocity from energy using relativity can also be obtained as follows.

$$ E_{kin} + m_0 c^2 = \frac{m_0 c^2}{\sqrt{1-\left(\frac{v}{c}\right)^2}} $$ $$ v = c\sqrt{1-\left( \frac{1}{\frac{E_{kin}}{m_0 c^2} +1} \right)^2} $$

The energy loss of the detector placed on the beamline is then calculated and the PID diagram is obtained by plotting the possible measured values using these relationships.

Usage

First, please prepare the SRIMlib dataset. You need all input ion for “mylar” and “Si” target energy loss table. For the SRIMlib setting, please refer this page.

Next, you need input ions and beamline parameter files. The format is like this.

​
input_ions:
  - name: 7Li3
    charge: 3
    mass: 7.01435758 # amu
    color: 0 # 0 -> red, 1 -> blue, 2 -> black
  - name: 6He2
    charge: 2
    mass: 6.01778863
    color: 1
  - name: 3H1
    charge: 1
    mass: 3.015500905
    color: 2
  - name: 2H1
    charge: 1
    mass: 2.013553496
    color: 2
  - name: 1H1
    charge: 1
    mass: 1.007276452
    color: 2
  - name: 4He2
    charge: 2
    mass: 4.001506094
    color: 2

# BLD parameters
f1_parameters:
  brho: 1.227 # Tm
  rf_period: 57.0 # ns

f2_parameters:
  PPAC_thickness: 10.0 # um, mylar
  SSD_thickness: 1500.0 # um

f3_parameters:
  a_thickness: 15.0 # um, mylar, PPACa/MWDCa
  b_thickness: 15.0 # um, mylar, PPACb/MWDCb
  distance: 290.5 # mm, between two tracking detectors
  trigger: 0 # PPACa/MWDCa -> 0, PPACb/MWDCb -> 1

# display parameters
f2_display:
  rf_offset: -6.5 # ns
  rf_range: [0.0, 120.0] # ns
  energy_range: [0.0, 100.0] # MeV

f3_display:
  rf_offset: -12.0 # ns
  tof_offset: -2.7 # ns
  rf_range: [0.0, 120.0] # ns
  tof_range: [0.0, 8.0] # ns
Info

You can add the beam ions freely, but you need to prepare SRIM Output table.

Lastly, let’s prepare the steering file. If you want to do only PID calculation, you can use chkpid.yaml.

​
Processor:
  - name: pid
    type: art::TCRIBPIDProcessor
    parameter:
      FileName: prm/pid/expname.yaml
      Batch: false
      OutputTransparency: 1

You can add these sentences for any other steering files. I think it is useful when you want to overlap the data figure and calculation figure. If you set Batch: false, the canvases for F2 PID and F3 PID will appear automatically. Batch: true is quiet mode.

This is an example of the automatically generated figure.

The process for the calculation is performed in init process (I mean not event loop), so when you add the steering file, the figure will be created.

> acd
> a
artemis [0] add steering/chkpid.yaml
# process is performed now
# if Batch: false, the two PID figure will appear automatically 

artemis [1] ls

 artemis
>   0 TDirectory pid             pid       

artemis [2] cd 0
artemis [3] ls

 pid
>   0 TMultiGraph                 F2_PID; F2 RF [ns]; F2 SSD [MeV]
    1 TMultiGraph                 F3_PID; F3 RF [ns]; PPACs/MWDCs TOF [ns]
    2 TCanvas F2_canvas       F2_canvas 
    3 TCanvas F3_canvas       F3_canvas 

artemis [4] draw 0
Info

There are two kinds of object, TMultiGraph and TCanvas. The ht command cannot draw these object, so I also made draw command to be able to draw “TMultiGraph” objects.

HOWEVER, even this “draw” command cannot display the “TCanvas” object yet… If you save the object using hstore command or check from THttpServer, you can check the TCanvas objects.

This “TMultiGraph” object is useful when you want to overlay th data.

artemis [*] ht something # this is gaussian example
artemis [*] dr 0 p same