1. HL-LHC HEL BPM

2. Outline: Specifications reviewed Summery of last presentation
Strip line BPM
LF Acquisition systems
Summary

3. HEL BPM Specifications:
Functional specifications :
E_beam off/on, 1 to 3 times per turn
No high frequency modulation!!
Injection and high energy stable beams
Single bunch and full machine
Proton beam
Electron beam
Comments
Intensity
5E9 (2.1A) / 2.5E11 (63A)
1 / 5A
Bunch / Pulse length
1ns
1-86us
P=4σ; E_beam off 3us; tr = 200ns
Relativistic β 1
Resolution
100um / 20um
Relative accuracy
100um
Between beams
Absolute accuracy
500um
Max beam displacement
4mm
Time resolution
228t orbit
1 per turn ?
Inner diameter
60mm
Max. outer diameter
120mm
DN63 flanges=114mm

4. No magnetic components!
BPMs for Hollow Electron Lens
No magnetic components!

5. Principle: Same BPMs for the two beams to minimize mechanical offsets
Same electronics for the two beams to minimize electrical offsets
Time separation
Measure EBeam in abort gap (and elsewhere) WHEN switched off / on and NO PBeam present
Measure PBeam elsewhere
Low frequency:
40MHz for Proton beam
< 1MHz for Electron beam

6. BPMs considered: Present HEL BPM design Button BPM
L= 100mm, ϕ=75⁰; C=20pF, R=50Ω
D= 24mm; C=8pF; R=50Ω
FNAL TEL 2 BPM

7. Beam Signals: Proton Beam: Electron Beam: σ=0.25ns, N=2.5E11, 25ns
40MHz lines
Electron Beam:
1 to 86us; 1 to 5A
Tr=200ns

8. Wide band Beam signals with electrostatic BPM
200Vp
Protons :
I= 63A, 25ns
Frequency (Hz)
Response (V)
~160MHz
(20pF, 50Ω)
0.8Vpp
Electrons :
I= 5A,
Tr=200ns,
Off/on 2us
EBeam
Off / on
EBeam spectrum heavily filtered

9. With 25MHz LP filter Electrostatic BPM Button BPM
Amplitudes shown for max currents
0.8Vpp
Button BPM
0.8Vpp
Electrostatic BPM is better suited for the LF version,
10 times more signal

10. 23 degree strip line, ID=61mm
~1.15db/mm
Design criteria: Minimize Proton beam signals (< 100V), maximize Electron beam signals

11. 23 deg. 400mm Stripline Gaussian Proton bunch
Select first harmonic and filter

12. 23deg, 400mm, Stripline with electron beam on/off

13. LHC Stripline: LHCBPLX
ID = 80mm, 23.2 degree 400mm electrodes
DN100
Could be scaled to ID 60mm, with DN62 flanges

14. BPM signal summery
BPM
Electron beam on/off
Gaussian 2.5*10^11, 0.25ns
Gaussian,
2.5*10^11 with ~25MHz LP filter
Button
0.04vp
63Vp
~0.65V
Strip line (0.2m, 45⁰)
0.22Vp
200Vp
~0.45Vp
Strip line (0.4m, 23⁰)
0.2V
100Vp
Electrostatic (75⁰)
0.8Vp
~200Vp
~0.4Vp
Stripline followed by 25MHz lowpass filter good solution!

15. Acquisition system: DOROS

16. Acquisition system: VFC

17. Summary: BPM choice: Low frequency acquisition system:
Strip line BPM (Shorted)? (L=400mm, ϕ=~20⁰) is best choice for LF system, and would be good for HF system as well.
Buttons not well suited for LF system
Integration and CST simulations next steps
Low frequency acquisition system:
DOROS or VFC?