Implementation of Transimpedance Analog Front – End
Card for Los Alamos Neutron Science Center
Accelerator Wire Scanners
D. Rai†, H. Leffler, S.A. Baily, D. Zimmermann, L. Montoya, L. Kennel, D. Martinez, J. Duran, A. Braido | Los Alamos National Lab, Los Alamos, NM 87545, USA

Abstract
The Los Alamos Neutron Science Center’s(LANSCE) Accelerator Operations and Technology
division - Instrumentation and Controls (AOT-IC)
team executed a project that implemented a new
Analog Front-End (AFE) card for their wire
scanner’s Data Acquisition (DAQ) system. The AFE
accommodates the signal amplification and noise
reduction needed to acquire essential measurement
data required for beam diagnostics for LANSCE
accelerator. Wire Scanners are electro-mechanicalbeam interceptive devices that provide crosssectional beam profile measurement data fitted to a
Gaussian distribution that is then extrapolated toprovide beam shape and position. The beam shapeand position information allow the operator to adjust
parameters such as acceleration, steering, andfocus to provide optimized beam delivery to targets.
The project included software and hardware
implementation that eliminated the dependency on
legacy systems and consolidated various AFE
designs for diagnostics systems into a single design
with 11 gain settings ranging from 100nA to 40mA at
10V full scale to accommodate its futureapplications on other diagnostics systems.

Figure 3: New TIA AFE Assembly

Figure 2: Single Channel Layout of New Transimpedance AFE

Need for New Design

Figure 6: LBEG Beam scan of TRWS07
Wire Scanners

During the implementation of the QAC (QuadActuator Controller) and DAQ system for wire
scanner systems in the transition region and downstream areas, the LANSCE Harp AFE was used.
The LANSCE Harp AFE was adequate inperforming wire scanner scans of the LBEG (LongBunch Enabled Gate) beam but not for MPEG
(Micro Pulse Enabled Gate).
LBEG is a higher current beam with 50 times
greater macro pulse average current and 100 times
greater charge per pulse than MPEG

Figure 4: LANSCE Site Map (Line D North)Figure 7: MPEG Beam scan of LDWS3X andLDWS3Y Wire Scanners

Conclusion

Figure 1: Wire Scanner and Sensor Fork
Assembly

Final Design
Based on Transimpedance Amplifier (TIA) circuitdesign to convert and amplify low current output ofsensors to usable output voltage level.
The design includes 11 selectable gains divided
between seven high and four low bandwidths.
Figure 2 shows the final single-channel layout of theTIA circuit and Fig. 3 shows the final fabricatedassembly of the new AFE design.

Figure 5: Wire Scanner System Block Diagram

During the V&V (Verification and Validation) of thenew AFE, hardware and software implementation it
showed that the new Transimpedance AFE designfor the DAQ system met all the design
requirements. Figure 6 and Fig. 7 show successful
wire scanner scans with LBEG and MPEG beamtaken during beam development time. Both scansshow a good Gaussian fit with a clear beam centerand size for horizontal and vertical axes providing
essential data for beam tuning. The new design has
adequately addressed design and functional
limitations of the LANSCE Harp AFE providing a
dynamic gain range to measure the induced sensor
current with accuracy and stability.

_______________________* This work was supported by the U.S. Department of Energy through theLos Alamos National Laboratory. Los Alamos National Laboratory isoperated by Triad National Security, LLC, for the National NuclearSecurity Administration of U.S. Department of Energy (Contract No.
89233218CNA000001). † drai@lanl.gov, LA-UR-23-30119

Managed by Triad National Security, LLC, for the U.S. Department of Energy’s NNSA.

LA-UR-23-30119