1. ESS | A Preliminary Feasibility Assessment of Power Converters and Magnets for Beam Raster System| 2012-03-14| Carlos A. Martins, ESS Preliminary Feasibility Assessment of Power Converters and Magnets for Beam Raster System Carlos A. Martins ESS, Accelerator Division 1

2. ESS | A Preliminary Feasibility Assessment of Power Converters and Magnets for Beam Raster System| 2012-03-14| Carlos A. Martins, ESS The (APT) Concept Features: -4 Horizontal Dipole Magnets; 4 Vertical Dipole Magnets (in principle all identical); -8 independent power converters (modulators), all identical; -Magnet technology: Ferrite cores, water cooled copper windings; -Power converter technology: IGBT based H-bridges (600V, 100A); -Continuous (CW) operation; 2 Cables (coaxial or tri-axial) Power converters/current generators (triangular current waveforms) 4 H + 4 V fast AC dipole magnets

3. ESS | A Preliminary Feasibility Assessment of Power Converters and Magnets for Beam Raster System| 2012-03-14| Carlos A. Martins, ESS ESS Raster system Features: -4 Horizontal Dipole Magnets; 4 Vertical Dipole Magnets (in principle all identical); -8 independent power converters (modulators), all identical; -Pulsed Linac (duty-cycle = 5%) -> PULSED RASTER SYSTEM; -Magnet technology: Ferrite cores, Air cooled copper windings (Litz wire to reduce eddy currents); -Power converter technology: IGBT based H-bridges (<1kV, <1kA); -Ceramic vaccuum chamber (< 1m length/section) with metallic RF coating (thickness: < 1 μm ??) 3 < 1 m Raster Dipole magnets Side view of the raster beam line Vaccuum chamber (ceramic) section flange

4. ESS | A Preliminary Feasibility Assessment of Power Converters and Magnets for Beam Raster System| 2012-03-14| Carlos A. Martins, ESS Main Parameters of the Raster System (*) (source: Heine Thomsen – Aahrus University) -Number of magnets (H+V): 4+4; -Total beam deflection (H & V) (*) :1.81 mrad; -Beam deflection, per magnet (H & V) (*) :0.453 mrad; -Beam rigidity:11 T.m; -Field accuracy (H & V):1 %; -Max. raster frequency (H & V) (*) :20 kHz 4 Beam spot trajectory (example) time Bx 0 1 2 3 4 5 6 7 8 9 Bx max -Bx max By By max -By max Magnetic field waveforms in H (x) and V (y) dipoles (*) x and y deflections considered identical for simplicity (square raster footprint) x y x max -x max y max -y max 0 1 2 3 4 5 6 7 8 9 raster footprint

5. ESS | A Preliminary Feasibility Assessment of Power Converters and Magnets for Beam Raster System| 2012-03-14| Carlos A. Martins, ESS Characteristics of Raster Magnets From the former Main Parameters table: 5 “Double-C” core I : coil current; N: number of turns; g : height of the air gap; w c : width of the air gap core; w g : width of the flux in gap (w g =1.3*w c ); l : magnetic length (3 rd dimension); B g : Field density in the gap; L : Magnet inductance: “C” core g wcwc wgwg N I I l vacuum chamber Magnetic core winding

6. ESS | A Preliminary Feasibility Assessment of Power Converters and Magnets for Beam Raster System| 2012-03-14| Carlos A. Martins, ESS Analytical Dimensioning of Raster Magnets (from Heine Thomsen inputs) From the former Main Parameters table: -Magnetic length, (H & V): 300 mm; -Magnet air gap height, (H & V):100 mm; (80 mm chamber inner diameter) -Magnet air gap width (H & V):100 mm; (80 mm chamber inner diameter) -Field amplitude, Bx max /By max (H & V) (*) :17 mT (compatible w/ ferrite core); -Magnet current amplitude, peak:440A; -Magnet coil number of turns:3; -Effective magnet air gap cross section:= 1.3*0.1*0.3 = 0.039 m 2 ; -Magnet inductance:4.45 μH; -Cable inductance:6 μH; (20m distance) -Magnet coil cross section:11 mm 2 ; -Magnet coil length:2.4 m; -Magnet coil resistance:4 mΩ; -Magnet coil losses during pulse flat-top:388 W; -Magnet coil losses (average, 5% duty-cycle):19.4W; (compatible w/ air cooling, Litz wire) 6 Note: All calculations are in magneto-static conditions; effect of eddy currents neglected;

7. ESS | A Preliminary Feasibility Assessment of Power Converters and Magnets for Beam Raster System| 2012-03-14| Carlos A. Martins, ESS Characteristics of Power Converters From the former Main Parameters table: 7 DRIVER CAPACITOR CHARGER COAX CABLE VCVC + - DRIVER CAPACITOR CHARGER COAX CABLE VCVC + - X 8 time I I max -I max time V VCVC -V C Control flexibility: -Adjust Vc, i.e. the dI/dt (slope); -Choose all switching instants; (choose frequency and current amplitudes) But: -Positive slope = negative slope; -Impossible to adjust the slopes inside a beam pulse, but possible from one pulse to the next one;

8. ESS | A Preliminary Feasibility Assessment of Power Converters and Magnets for Beam Raster System| 2012-03-14| Carlos A. Martins, ESS Dimensioning of Power Converters From the Magnets & cable parameters table: -Output voltage (peak): = (L mag +L cable )*dI/dt = +/- 370 V; -Output current (peak):+/- 440A; -Max. switching frequency:20 kHz (3.5ms / 14 Hz); 8 -Straightforward design; -Dimensions: 19” rack, 3U height, 600mm depth; -Cost per power converter: < 5 kEURO (*) ; -Cost of the entire power supply system (including controls): < 50 kEURO (*) ; (*) : does not includes development costs

9. ESS | A Preliminary Feasibility Assessment of Power Converters and Magnets for Beam Raster System| 2012-03-14| Carlos A. Martins, ESS Conclusions Technical: -Effect of the vacuum chamber coating thickness on the field distortion; -Controls of the power converters, assuring raster pattern quality; -Interlocks (Beam interlocks, field interlocks, current interlocks); -Redundancy ? If yes, how to manage it ? Organizational: -Prototyping ? Testing without beam / with beam ? -Development plan ? 9 Open points -Power converters and raster magnets seem feasible at moderate costs; -Use of ceramic vacuum chambers (< 1m) would be preferable wrt vacuum tanks; -2 raster magnets per chamber section leads to total length = ~ 4 m (optimization still possible); -Power converters should be placed in a place such that cable lengths to magnets < 20 m;