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Ideal location of energy spread measurements in the linac4-PSB transfer line

Ideal location of energy spread measurements in the linac4-PSB transfer line. Alessandra L ombardi. introduction. Distances involved in meters Reminder: 1 m in linac2 = 2 m in LINAC 4 !!!

susanna-rufus
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Ideal location of energy spread measurements in the linac4-PSB transfer line

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  1. Ideal location of energy spread measurements in the linac4-PSB transfer line Alessandra Lombardi BCC 46-alternative to the LBS line

  2. introduction • Distances involved in meters • Reminder: 1 m in linac2 = 2 m in LINAC4 !!! • If we re-scale from linac2 we could measure the en spread about 100m before PSB injection, let’s call this point “point F”. BCC 46-alternative to the LBS line

  3. LINAC4 at PSB injection-specs • Average energy : 160 ±?? • Energy swing over 20 µsec: 1.2 MeV • Energy spread : min 0.120 MeV BCC 46-alternative to the LBS line

  4. Energy….. • TOF via 3 BPM and phase pick ups • we have 3 x 28 deg + 2 X 15 deg + BHZ20 and BHZ30 : we can measure the energy from the linac and find the zero crossing of the cavity • Line dispersion is very sensitive to Quadrupole(s) in the first horizontal bending. There are 3 beam centre position measurements before the vertical bending. BCC 46-alternative to the LBS line

  5. And energy spread… • This varies along the line due to : • Cavity in L4T line (L4T.ACDB.1075) :PIMS-like ; 700 kV effective voltage available. • Space charge : peak space charge in the RF bucket, it doesn't depend on the chopping factor, it depends on the source current and the losses along the linac. BCC 46-alternative to the LBS line

  6. What happens to energy spread along the line- effect of the cavity BCC 46-alternative to the LBS line

  7. Zoom in after the cavity – see effect of space charge BCC 46-alternative to the LBS line

  8. Comparison with LINAC2 BCC 46-alternative to the LBS line

  9. measuring≠controlling • The quality of the beam that we deliver to the PSB depends on • Linac4 RF settings and their control (phase and ampli jitter) • The available field in L4T.ACDB.1075 • With the present layout we can match the specs of the PSB : energy swing (±1.2 MeV over 20-40 µsec); rms energy spread variable 120keV-700 keV • If we need to reduce the energy spread or if we want to guarantee more control under different conditions we should ask for more power in the buncher and/or a second buncher but we cannot improve the situation with a more precise measurement! BCC 46-alternative to the LBS line

  10. Conclusion • It is possible to measure the energy spread of the beam before the LT LTB line and deduce sound values for the energy spread delivered to the PSB • This opens the possibility to measure the energy spread with different techniques than a bending magnet, which are more suitable for our layout and increased beam energy. BCC 46-alternative to the LBS line

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