Beam Monitoring

1
Beam Monitoring

• Basis for Discussion only
• Beam Rate
• Beam Profile
• Beam Normalization

2
Beam Parameters

• ? Available Parameters
• Phase Space parameters (x, x, y, y, p, ?p)
• µ- e- intensity Rµ, Rbeam e, RMichel e
• µ stopping fraction Rµ stop

3
Beam Rate Profile

• Indirect possibility
• measured by Michel e reconstruction using TCs
  DCs
• see Normalization
• (Rµ ? Accp), (Rµ Stop? Accp)
• (x0, y0)

y

• Direct possibility (hardware)
• measure Rµ via (x, y )
• RAPD at centre using
• APD-array mounted on inside
• of insertion bellows
• (i) Bellows Extended (x0, y0, Rµ) directly (1
  per day C-W Calib.)
• Disadvantage target must be moved
  calibration only !
• (ii) Bellows Retracted Michels only ! RZ ? Rµ -
  monitoring
• Disadvantage constant of proportionality
  must be measured

x
x
4
Beam Rate Profile - cont.

• Direct possibility (hardware) - cont.
• measure Rµ ? (x, y ) using fast, extremely
  thin MWPC
• Rµ via current calibration, (x, y) via
  calibration- monitoring
• (i) only possible at entrance window no
  vacuum
• Disadvantages (xZ , yZ ), radial Bfield
  component,
• gt multiple scattering, rate problematic,
  potential background

• Typical characteristics
• (100x100) mm2, 1mm wire spacing, 2.5mm half-gap
• x- y-wire planes, 3 cathode foils (12.5µ), 2
  shielding
• foils (25µ)
• 70 CF4 30 i-C4H10
• live Profile readout type, charge integration
  clocked
• discharge
• Examples µLAN (10x lower rate)
• MEG profile Chamber (too thick
  µ stop)

5
Beam Rate Profile - cont.

• Direct possibility (hardware) - cont.
• upstream, backward-pointing scintillator
  telescope for Michels
• from µ-decays-in-flight beam polarization
  favours backward
• decays, Rµ via calibration RTel ? Rµ -
  monitoring
• (i) only possibility between (Triplet
  II-BTS) ?
• Disadvantages potential background due to
  re-scattering of
• discarded beam e from Separator, at
  collimator system
• Active Target would be ideal,
• polystyrene good material C6H5CHCH2 a
  0.05
• Disadvantages rate requires segmentation,
  light difficult to extract
• Active Degrader only possible at centre BTS
  (double waist), MS
• Disadvantages rate requires segmentation,
  light difficult to extract,
• Bfield

6
Beam Normalization

• Need signal ? Rµ Stop
• Proton Signal accelerator -105 counts/mAs, good
  monitor,
• used for normalizing previous mentioned Rµ
  measurements
• Disadvantage depends on p-beam centring Tg.E
  long-term
• fluctuations 10, doesnt measure
  µs
• Measurement via Michel e spectrum (edge) from
  DCs TCs
• Using event Integration assuming V-A form of
  spectrum
• ? Rµ Stop ? Nµ Accp
  calibration monitoring
• Advantage Accp is same for µ?e? events
• further food for thought
  necessary