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

G. Velev 1/24/ 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 ~ a new type AC dipoles are needed These dipoles will be used to extinguish the protons at the level of 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.

G. Velev 1/24/ 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 kHz More information – Eric Prebys note: bin/RetrieveFile?docid=709 bin/RetrieveFile?docid=709 Collimator Out of time beam In time beam dipole

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

G. Velev 1/24/ 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

G. Velev 1/24/ 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 25 C Resistivity (  -m) Thermal Conductivity (W/K/m) Sample plate 10 RTDs 200x200x10 mm 3 200x200x5 mm 3

G. Velev 1/24/ Test system

G. Velev 1/24/ ANSYS simulation Magnetic flux directionTemperature Distribution

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

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

G. Velev 1/24/ kHz MnZn, 300 kHz, 1 plate Current A-turns B max (G) B begin (G) B end (G) T max (C) MnZn, 300kHz, 2 plates

G. Velev 1/24/ MnZn, 5.1 MHz, 2 plates 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)

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

G. Velev 1/24/ NiZn, 5.1 MHz, 1 plate Current A-turns B max (G) B begin (G) B end (G) T max (C) NiZn, 300 kHz, 1 plate

G. Velev 1/24/ 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

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

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

G. Velev 1/24/ 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.