12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3

IBIC2023, Saskatoon, Canada
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A. Walker, E. Kerstiens
Los Alamos National Laboratory, Los Alamos, NM, USAAbstract
The Los Alamos Neutron Science Center (LANSCE)
completed upgrades to its 1L Target Facility, which included installing the new Mark IV target assembly. Thisadded a third tungsten target located upstream of the othertwo targets. Prior to Mark IV, beam centering on target wasachieved by using thermocouples mounted to the quadrants
and center of the upper target coolant chamber. It is slightly
offset from center of the old upper target and it shadowsseveral of the thermocouples previously used to centerbeam on target. This required adjustments to the diagnostic
tools utilized to monitor position of the H- beam that is being delivered to the 1L target. The original display included
the thermocouple readouts and displayed a visual beamprofile and position taken from an upstream harp. With
some of the thermocouples now being shadowed, an image
overlay was added to show where the harp’s measured
beam position is relative to both the upper and middle targets. This gives the beam operations team an additional
level of awareness when it comes to thermocouple temperatures, beam steering, and beam tuning. Details of the display tool and its associated upgrades are presented.

INTRODUCTION
1L HARP Purpose
The purpose of the 1L Target [1] HARP is to provide aprofile of beam location as it strikes the target stack. The
HARP works in tandem with wire scanners to assist the operations team in beam tuning and loss minimization. TheHARP is an extremely valuable tool since the new MarkIV target has been installed. The HARP has a similar program to the wire scanners to show beam position.

1L HARP Diagnostic Display Purpose

constant updates to the beam position. The 1L HARP data
can be utilized in a Gaussian fit algorithm to provide abeam position and intensity map. Figure 1 below shows the1L HARP assembly and wire harness that is part of the 1LTarget assembly.

Figure 1: 1L HARP Diagnostic Assembly.

WIRE SCANNERS
1L (Target 1) wire scanner 1, 2, and 3 provides a pictureof the beam profile as it is being directed to the target, but
don’t provide a “live” status of the beam in the event of atune change. They utilize a single wire inserted in steps inorder to get a beam profile. This “live” status is extremely
important, and the wire scanners cause significant beam
spill making them ineffective for the information needed tovisualize. Figure 2 shows a wire scan performed to showbeam position in the X and Y axis.

The 1L Target HARP Display is an aid to the operations
team to provide a graphical representation of beam position. The display aggregates the data from the 1L HARPand utilizes a Gaussian distribution algorithm to provide a“heat map” graphical representation. The display also
shows a set of thermocouples that are utilized to further
analyze the beam position and intensity.

1L HARP CONSTRUCTION
The 1L Target HARP diagnostic is a set of wires spaced
out in the beam line in a grid formation to gather a beamprofile. An electrical current is induced in them proportional to beam intensity, which shows the beam profile similar to the wire scanners. The upside to the HARP is it isconstantly in the beam line and due to that can be provide*Work supported by the U.S. Department of Energy, Contract
No. DE-AC52-06NA25396

Figure 2: Wire Scanner Diagnostic Tool.
MOP03302 Beam Position Monitors

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1L TARGET HARP DIAGNOSTIC DISPLAY TOOL*

12th Int. Beam Instrum. Conf.
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IBIC2023, Saskatoon, Canada
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NEW MARK IV TARGETThe Mark IV target was installed during the beam outage in 2022. Initial testing and commissioning was performed during the beam run cycle for 2022, and beam on
target from 60 to 85 microamps. 2023 expects to see fullproduction beam of 90+ microamps. Installation of the newtarget required some changes to the diagnostics to better
serve the operations team with applicable information. Better analysis of the diagnostics and indications that the operations team needs will continue to be done to further improve the ability to tune the beam on the target.

Target Assembly
Three different target assemblies are utilized to provide neutrons to up to 15 different flight paths for experiments at varying energies. The upper target sits verticallyand is housed in tungsten, so getting an accurate picture of
the beam profile is key due to thermocouple shadowing andneutron moderation. Below the upper target is the Middle
Target which is surrounded by a reflector constructed ofberyllium. The lower target also has a liquid hydrogenmoderator to further thermalize neutrons being sent to theflight paths. Beam passes down through the top of the assembly and strikes the vertically aligned Upper Target Assembly before passing to the Middle and Lower targets.
Figure 3 shows the entire Mark IV Target assembly and its
associated components, while Figure 4 (across) shows theupper target assembly portion of the Mark IV Target.

Figure 4: Mark IV Upper Target Assembly.

Thermocouples
Thermocouples are placed in a cross pattern below theupper target assembly to aid operations in determining boththe location of the beam striking the target and the intensityof that beam. With the old target assembly there was nothing to “shadow” the thermocouples and potentially hidesome of that intensity, so when the Mark IV Target was installed there needed to be some adjustments in order tomake operations aware of this beam “shadowing”. In thecenter of the target assembly is the tungsten upper target
assembly shadowing the center, half of the lower, and aportion of the upper thermocouple. To the left of the tungsten upper target assembly is water that is shadowing theleft, and roughly half of the upper thermocouple. There isno shadowing of the right thermocouple, so reliance solely
on thermocouple indications for beam position would behighly unreliable due to three different densities of material
covering the different thermocouples.

1L HARP DISPLAY TOOL
The 1L HARP Display Tool is a graphical representationof beam position. It has been in use since 2019 to give theoperations team a constantly updating picture of beam position on the 1L Target. It has graphical representations forthe thermocouples, vertical upper target assembly, and thewater moderator. Thermocouple temperature indications
are also shown on the tool to assist operations in beam tuning. Below is a snapshot of the tool without any beam position indication. The pink color is the beam pipe (the circle) and the thermocouples (squares arranged in the crosspattern), the gold color in the upper left in the diagonal
shape is the water moderator that is shadowing some thermocouples, and the silver color is the vertical tungsten upper target assembly. Off to the right and the far left is air.
Prior to the Mark IV Target installation, there was no needto aid the operations team with this sort of overlay. TheHARP tool and wire scanners were sufficient in providing
an indication of beam position. However, once the new target was installed, modifications had to be made to ensure
Figure 3: New Mark IV Target.
MOP03310002 Beam Position Monitors

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ISSN: 2 6 7 3 - 5 3 5 0d o i : 1 0 . 1 8 4 2 9 / J A C o W - I B I C 2 0 2 3 - M O P 0 3 3that the correct indications were being utilized due to thermocouple shadowing affecting the temperature indications. Figure 5 is a screenshot of the 1L HARP Display tool
without beam on.

Figure 5: 1L HARP Display Tool (Without Beam).

1L Harp Display Tool (With Beam)
The 1L Harp Display Tool retrieves the HARP data fromthe EPICS control system and performs a Gaussian fit algorithm to determine the beam position for both the horizontal and vertical positions. This algorithm also determines beam intensity, so a very beneficial indication ofboth beam location and intensity is provided as an overlay
to the thermocouples. This overlay, in addition to the thermocouples and wire scanners is what the operations teamutilizes to tune beam as it reaches the 1L Target. The next
image is an image with simulated beam position, in orderto provide a visual representation of similar to what the operations team would see when tuning. The beam profile
would look significantly smaller and would be within thepink circle, but this is a good representation of both the position indication and intensity indications the Gaussian algorithm provides. Figure 6 has simulated beam placed on
it to show what the beam position indication looks like.

CHALLENGESFirst operation with the new Mark IV Target showed several challenges.
It was unknown how much shadowing the different materials would provide to the various thermocouples. To investigate this, beam was attempted to be centered on eachthermocouple to see how each reacted to a given current ofbeam placed on each. During this evolution, a new problem
cropped up that needed to be resolved first.
Steering the beam vertically towards the top thermocouple (the top thermocouple rose in temperature and the bottom lowered) gave the reverse indication with the HARP
data and the Gaussian indication (position indication
showed the beam moving towards the bottom thermocouple and away from the top thermocouple). This waschecked for the horizontal axis and found to respondproperly. After utilizing our other diagnostic tools, it wasdetermined that the HARP wires were likely wired backwards. To correct this, a software change was made to reverse the values in the array for the vertical axis. This corrected the position indication issue.

CONCLUSION
Further testing of the thermocouples to determine the extent of shadowing needs to be completed in order to better
aid the operations team. Adding the layer of indications forthe thermocouples and different moderators has been abenefit to the operations team with their efforts to reliably
deliver beam to a newer, smaller beam target.

REFERENCES[1] E. Kerstiens, “1L Target, Moderator, Reflector System,”
Reading, Los Alamos National Laboratory, April, 2023.

Figure 6: 1L HARP Display Tool (With Simulated Beam).
MOP03302 Beam Position Monitors

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12th Int. Beam Instrum. Conf.
ISBN: 9 7 8 - 3 - 9 5 4 5 0 - 2 3 6 - 3