1. A 3D design model of the apparatus for the Laser Wakefield Acceleration of electrons at ELI-NP
S. Balascuta1 , R. Dinca1
1) “Horia Hulubei” National Institute for R&D in Physics and Nuclear Engineering, Department of ELI-NP
Summary: The Laser Wakefield Plasma Acceleration (LWPA) of electron beams up to 38 GeV energy, is proposed by one of the experiments at "High Fields QED Physics" experimental areas at ELI-NP. An Electron Spectrometer will be used to measure the energy of the electrons. The ES is proposed here have a 1.6 m long Dipole Permanent Magnet [1] (inside the Interaction Chamber) and a Pulsed Electromagnet (B=5 Tesla, m long) outside the Interaction Chamber. One of the technical problems is the integration of this magnet with the geometry of the Interaction Chamber (IC) that has almost an octagonal shape with a 4.5 meters diameter. The assembly of two magnets comply with the space constrains. The magnets have to be lifted with the crane and aligned with the Laser beam axis . We present a 3D model of the apparatus (Interaction Chamber , Auxiliary Vacuum Chamber, CCD cameras with Scintillating Plates) proposed for the production and measurement of up to 38 GeV pulsed electron beam. Based on the Autodesk Inventor 3D model, we compute the total mass of the IC with its main components and of the Beam Dump. A three dimensional model of the main components of the LWFA apparatus (the two magnets, Interaction Chamber, CCD cameras and Imaging Plates) was built to study the integration of the different experimental components. Calculations of the magnetic field profile for a system of two Dipole Permanent Magnets were done in COMSOL. The data bandwidth was calculated based on the characteristics of the CCD cameras. The connection diagram of 16 CCD cameras with the computer is presented.
400
275
450
185 30
200
780
Turning Box
F/20
F/3 7 8 6 4 3 5 9 1 2
Fig. 6: The top-view of the Pump and Probe Laser Beams in 135o configuration. The dimensions are in cm. B
161 22 34 A 70 38
CCD
Fig. 1: A 3D Autodesk model of the two Laser beams (1 –Pump beam, 2-Probe beam), 3-Capillary Cell,
4 –Quadrupole Magnets, 5-Integrating Charge Transformer, 6-Permanent Dipole Magnets, 7-Pulsed Electromagnet, 8-Electron-Gamma Converter and 9-Beam Dump. C 85
100
150 4 5 6 3
Fig. 2: A three dimensional model of the two Laser beams (Pump beam – red, Probe beam –blue) , the Quadrupole magnets- 4, Integrating Charge Transformer -5, the Dipole Magnets -5 , are located inside the Interaction Chamber.
Fig. 7: Front (A), Top (B) and Lateral (C) views of the 1.6 meters long System of Permanent Magnets (with NdFeB magnets), Iron Yoke (Front and Lateral views) and CCD cameras. There are 14 CCD cameras (7 on top and 7 at the bottom of the System of Permanent Magnets located inside the Interaction Chamber. 7 8 9
Mass calculation of the E6 Interaction Chamber with the main experimental components
Component
Volume
(cm3)
Mass
(tons)
Beam Dump (Magnetite + Pb + Fe + Polyethylene)
20E6
147.3
Interaction Chamber (Walls + Roof + Windows)
10.596E6
28.715
Turning Box (Al +Glass) E6
1.062
Electromagnet (Fe + Cu + Al)
1.1668E6
0.610
Table Electromagnet (Al)
0.1631E6
0.442
Off-axis Parabola (Al + Glass)
0.357E6
0.940
Flat-Mirror (Al + Glass)
0.4446E6
0.996
Component
Volume
(cm3)
Mass
(tons)
Dipole Magnet1 (Al, NdFeB, Fe)
0.0434E6
Dipole Magnet2 (Al, NdFeB, Fe)
0.1369E6
Dipole Magnet 3 (Al, NdFeB, Fe)
0.1389E6
Quadrupole Magnets (Al, NdFeB, Fe)
0.0104E6
Table support for Dipole Magnets (Al)
0.1885E6
0.511
Optical Bench (Al)
0.3305E6
0.896
Fig. 3. The pulsed electromagnet -7 (without vacuum shield) with the Gamma Ray Detector (8) and support table (9) are located outside the Interaction Chamber.
Converter
Pulsed Electromagnet
Gamma Ray Detector 49 47
240 68
CCD cameras (from Basler )
Sensor CCD: ICX274AL
Resolution: x 1236 pixel
Read out rate: 20 frames/second
Bandwith: 702 Mbps
PC Network: GigE Card PCIe AdLink GIE62 + PoE, 2Ports
Switch: 2 x 8 ports with PoE
Fig. 4. The dimensions (in cm) of the electron-gamma Converter (with Gamma Ray Detector) and Pulsed Electromagnet located in the Auxiliary Chamber.
The magnetic field profile computed in COMSOL.
Conclusion
Total mass of the Interaction Chamber (IC) with its main components tons, is distributed over a surface of 19.1 m2 . The platform load (for the IC) is 1.9 tons/m2 . The mass of the beam dump tons is distributed over 8 m2 such that the platform load of 18.4 tons/m2 over this region. The maximum number of CCD cameras for the above design, is 20. If all CCD cameras are used, a Network Switch Box with 24 inputs and three DAQ Cards are required . A trigger signal from the High Power Laser Front End, is required to synchronize the CCD cameras with the Laser pulses. The Laser frequency is 1 pulse/minute. Each CCD can record up to 20 frames per second and has a bandwidth of 702 MB/second.
Fig. 5. Left Panel: The magnetic field component (Bx) is calculated along three lines parallel with the common axis of two Dipole Permanent Magnets DPM (1.5 m and 2.5 m long) made from NdFeB. The distance between the two DPMs is 20 cm . Right Panel: The field gradient dBx/dZ is calculated along the same three lines.
[1] S. Balascuta, “A rectangular electromagnet for the electron beam energy measurements”, submitted to Romanian Reports in Physics, 2015
[2] S. Balascuta , “Imaging properties and the electric power of a cylindrical electromagnet”, submitted to Computing in Science and Engineering”, 2015