Hofmann, K.

Reeg, H.

Schwickert, M.

Soliman, E.

GSI Repository

A novel DC current transformer using magneto-resistance sensors for FAIR E. Soliman1, 2, H. Reeg1, M. Schwickert1, K. Hofmann2 1GSI, Darmstadt, Germany; 2IES Institute, TU Darmstadt, Germany.A Novel DC Current Transformer (N-DCCT) for FAIR SIS100 is under development at GSI Beam Diagnostic department in collaboration with IES Institute of TU Darmstadt. DCCTs are used as non-intercepting standard tools for online beam current measurement in synchro-trons and storage rings. The working principle of com-monly used DCCTs is well known [1]. However, at cer-tain bunch frequencies in ring accelerators inaccurate readings are observed due to inter-modulation distortion. The N-DCCT senses the magnetic field created by the ion beam current, using Tunneling Magneto-Resistance (TMR) sensors. Also a closed-loop N-DCCT is currently under development.  TMR Sensor for N-DCCT Currently a N-DCCT based on TMR sensors is under development at GSI. The N-DCCT open-loop structure is shown in Figure 1 [2]. The main measurement principle is precise detection of the ion beam DC magnetic field by TMR sensors. In the present setup the TMR sensors from MultiDimension Company [3] are placed inside an air gap of a high permeability ferromagnetic ring core with 10 mm width (VITROVAC ‘6025F’). The value of the magnetic field inside the air gap is calculated according to the following formula: ogap PB Id      (1) Where Bgap is the magnetic field inside the air gap in Tesla, µo is the permeability of vacuum in Tm/A, IP is the beam current and d is the air gap width in m.  Figure 1: N-DCCT Open Loop Structure. The TMR’s output voltage is directly proportional to the ion beam current. A voltage amplifier is added to en-hance the N-DCCT resolution. Printed circuit boards were fabricated to compare the performance of different MR sensors. A test setup has been prepared for the N-DCCT as shown in Figure 2. A mechanical support was manu-factured to hold the flux concentrator. In addition a µ-metal box for shielding covers the whole N-DCCT test setup.  A DC current is generated in a conducting wire at the center of the core using a power amplifier and a signal generator. The value of the produced voltage from the power amplifier is ±32V. This will produce a ±0.32A in the wire. The value of the magnetic field intensity in the air gap of the core will be ±0.04mT. The output voltage of the TMR sensors is amplified with a voltage amplifier of gain 10.  Tests were carried out for two different TMR sensors, MMLH45F and MMLP57F. Figure 3 shows the output voltage of the N-DCCT versus input current for the MMLH45F. The slope of transfer characteristic is the sensitivity of the N-DCCT. The measured value from the experimental test is 0.566V/A, while the theoretical value is 0.75V/A. The sensitivity of the TMR sensor to the magnetic field is 0.453V/mT from the measurements and 0.6V/mT from the sensor’s datasheet. Measurements with the sensor type MMLP57F yielded a sensitivity of 0.275 V/A, compared to 0.31V/A (datasheet). The noise analysis for the system is currently under investigation.  Figure 2: N-DCCT Test Setup.  Figure 3: Output Voltage of the N-DCCT.  References [1] K. Unser, “A Toroidal DC Beam Current Transform-er with High Resolution”, IEEE Trans. Nuclear Sci-ence, NS-28 No. 3, June 1981   [2] M. Häpe et al., “High Dynamic Magnetic Beam Cur-rent Measurements ...”, DIPAC’05, May 2005, p. 102; http://www.JACoW.org [3] MultiDimension Technology Co., Ltd., (CN) [4] VACUUMSCHMELZE GmbH & Co. KG, (D).  _______________________________________  * Work supported BMBF project ID: 05P12RDRBG. #pt@desy.de FG-SIS100-11 GSI SCIENTIFIC REPORT 2014480 DOI:10.15120/GR-2015-1-FG-SIS100-11

A novel DC current transformer using magneto-resistance sensors for FAIR

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A novel DC current transformer using magneto-resistance sensors for FAIR

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