1. G. Velev 1/24/ 2011 1 Ferrite Tests for Mu2e Beam- Line Extinction Uses G. Velev Technical Division Magnet Systems Department

2. G. Velev 1/24/ 2011 2 Introduction Ferrite pulsed magnets are commonly used in the accelerator applications –kickers – injection, extraction, gap clearing (recently MI) –Orbump – beam orbit manipulation All of them have a low operational duty cycle, practically <1-3% For Mu2e, an experiment which searches for a μ-e conversion with an unprecedented sensitivity of ~ 10 -16 a new type AC dipoles are needed These dipoles will be used to extinguish the protons at the level of 10 -6 -10 -7 between the bunches. They should work continuously at 300 kHz ( B max = 160 G) and possibly at 5.1 MHz (B max ~ 10 G) at 100% duty cycle In 2009, we started a R&D to select suitable ferrites for these dipoles Collaboration with Japan, COMET experiment needs similar technology.

3. G. Velev 1/24/ 2011 3 Beam cleaning The idea is to synchronize the beam bunches and AC magnetic field 100 ns bunches separated with 1.7 μs gap ~ 600 kHz The bunches are moving on the nodes - 300 kHz More information – Eric Prebys note: http://mu2e-docdb.fnal.gov/cgi- bin/RetrieveFile?docid=709 http://mu2e-docdb.fnal.gov/cgi- bin/RetrieveFile?docid=709 Collimator Out of time beam In time beam dipole

4. G. Velev 1/24/ 2011 4 Beam cleaning: current version Time Dipole Field (G) Collimator Out of time beam In time beam dipoles 300 kHz 5.1 MHz

5. G. Velev 1/24/ 2011 5 B-H curve B =  H, in ferrites  =  (H,T(C), …) The losses in ferrite core ~ area under the B-H curve At low frequency - hysteresis loss At high frequency - eddy current loss B H P total

6. G. Velev 1/24/ 2011 6 Ferrite samples Ferrite types: MnZn, NiZn Frequency: 300kHz, 5.1MHz FerritesGeometry ferrite 10 mm «1 plate» geometry ferrite 10 mm isolator «2 plate» geometry Eddy Currents Material Properties · MnZn NiZn Rel.Permeabillity @ 25 C 6500625 Resistivity (  -m) 10 2 10 6 Thermal Conductivity (W/K/m) 4.54.3 Sample plate 10 RTDs 200x200x10 mm 3 200x200x5 mm 3

7. G. Velev 1/24/ 2011 7 Test system

8. G. Velev 1/24/ 2011 8 ANSYS simulation Magnetic flux density @ directionTemperature Distribution

9. G. Velev 1/24/ 2011 9 B-H curves - MnZn

10. G. Velev 1/24/ 2011 10 Heating comparison: 1 plate vs 2 plates MnZn Low eddy currents High eddy currents

11. G. Velev 1/24/ 2011 11 MnZn@300 kHz MnZn, 300 kHz, 1 plate 0.5 60586022.7 1.2 16815416631.6 1.8 24323019642.6 3.0 35634120165.0 4.1 40129720778.4 Current A-turns B max (G) B begin (G) B end (G) T max (C) MnZn, 300kHz, 2 plates 0.760 5422.3 1.417116415431.2 2.026825620236.5 2.734229623140.9

12. G. Velev 1/24/ 2011 12 MnZn@5.1MHz MnZn, 5.1 MHz, 2 plates 3.25.84.25.323.3 7.210.49.29.832.9 10.615.013.514.046.9 17.921.120.618.777.4 Current A-turns B max (G) B begin (G) B end (G) T max (C) Current A-turns B max (G) B begin (G) B end (G) T max (C)

13. G. Velev 1/24/ 2011 13 B-H curve - NiZn

14. G. Velev 1/24/ 2011 14 NiZn, 5.1 MHz, 1 plate 3.36.04.95.521.7 9.69.98.59.428.0 12.311.710.611.237.2 13.712.311.410.742.4 25.118.918.712.465.2 NiZn@5.1MHz Current A-turns B max (G) B begin (G) B end (G) T max (C) NiZn, 300 kHz, 1 plate 3.6 64 61 64 23.5 5.71021019528.3 7.814614311140.1 9.316716011673.2

15. G. Velev 1/24/ 2011 15 Ferrite selection Both materials satisfy the criteria for magnet strength Due to the low resistivity and large eddy current effect, the thickness of MnZn ferrite plates should be ~ 5 mm. At such high frequencies and power, for MnZn plate we need good insulator between ferrites and power bus - problem with insulation due to corona discharge

16. G. Velev 1/24/ 2011 16 Magnet design - x-section Two designs were considered – magnet with C and H shape of the ferrite plates. IEEE Applied Superconductivity, v. 20, p. 1642.

17. G. Velev 1/24/ 2011 17 Current Model Design Beam direction NiZn Ferrite plates

18. G. Velev 1/24/ 2011 18 Summary We measured MnZn and NiZn ferrite samples at 300 kHz and 5.1 MHz. Both materials will satisfy the AC dipole requirements. Building a magnet prototype based on the selected NiZn ferrites – simple design due to the high resistivity of the material and no-insulation between the ferrites and copper bus This summer – we plan to test the prototype, including 5.1 MHz Depending on the result an iteration may be needed. Contributions: V. Kashikhin, S. Makarov, D. Harding, E. Prebys and PARTI students: I. Iedemska and E. Bulushev.