# Presentation: 782953

## Horn Alignment Cross-hair System

- NuMI Horn Alignment Cross-hairs
**Target Hall Instrumentation Review**
**November 18, 2002**
*David Ayres*
*Argonne National Laboratory*
*WBS 1.1.2 co-Manager*

_**Outline**_
-  Description, specifications
-  Status and remaining work
-   Summary

## Cross-hair Alignment System

- The cross hairs are three sets of horizontal and vertical strips of aluminum attached to the ends of Horn 1 and Horn 2
- Horizontal and vertical scans are performed with the low intensity proton beam across each set of cross hairs (target/baffle out)
- Protons scattered by cross hairs are detected by Beam Loss Monitors (BLMs) downstream of Horns 1 and 2
- BLMs read out through ACNET
- BLMs offset from beam centerline by 30 cm to avoid damage during high intensity running
- Each set of cross hairs is offset from beam centerline by +2.5 mm or –2.5 mm, both horizontally and vertically
- To distinguish the signals from different sets during scans
- To avoid damage by high intensity beam
- The upstream end of Horn 1 cannot have cross hairs but its location will be determined by scanning the neck of the horn inner conductor

## Target/Baffle/Horn-1 Cross-hair Geometry

- Water tank

- Stripline

- Baffle

- Target

- Target/Baffle
-     Module

- Horn 1 Module

- Horn 1

- Carrier

- Horn 1 neck

- Cross hair #1

- BLM #1

- Target and Baffle move out of beam for cross-hair scan

## Cross-hair Geometry for Horns 1 and 2

## Cross-hair System Simulations

- MARS beam heating calculations determined that cross hairs made of 1-mm wide aluminum strips would not overheat during full intensity running
-  NuMI-882, Byron Lundberg
- GEANT simulations determined the thicknesses of cross hairs needed to give good scan signal-to-noise (0.6-0.8) in BLMs: #1 and #3 are 12 mm thick, #2 is 36 mm thick
-  NuMI-864, Debbie Harris
- The NuMI-864 GEANT simulation also showed that
- A scan of the Horn 1 neck gives exellent signal-to-noise (>10)
- During normal running, cross hair scattering causes less than 0.2% changes in neutrino flux and in the ratio of near/far detector event rates

## Cross-hair System Specifications

- Proton beam instrumentation and control should permit scans at low intensity (1012 protons/pulse), 3.5 mm at cross hairs, 12 mm at Horn 1 neck.
- Beam scans should determine Horn 1 and Horn 2 transverse locations to at least 0.5 mm and 1.0 mm respectively.
- BLM response should be stable and sensitive to rate changes of ~5% at intensities expected during scans (107 particles/cm2/1012 protons/spill).
- Additional material in the beam (beyond that assumed in NuMI-864) will degrade signal-to-noise ratio in scans.
- Cross-hair material should not effect neutrino flux significantly (<1%).
- Cross-hair and BLM locations, materials are chosen to ensure survival during full intensity beam running.
- BLMs should be able to measure beam-pulse timing and targeting efficiency as a backup for target Budal monitor (after initial calibration against Budal monitor).

## Cost and Schedule

- The cross-hair task is approximately on schedule
- The cost estimate (CR #156, Feb. 2002) still seems OK

## Status and Remaining Work

- Complete engineering of cross-hair mechanical structures
- Complete engineering design and drawings
- Repeat simulations with final cross-hair and BLM configurations and locations
- Recheck calculation of beam heating with final geometry
- Build and test prototype cross hair sets
- Check mechanical stability during pulsing on Horn 2 in MI-8 during Spring 2003
- Test Horn 1 cross hairs in MI-8 during Summer 2003
- Build and install three production sets of cross hairs

## Summary

- Cross-hair and BLM designs are advanced enough to ensure that specifications are easily met
- We have a practical plan for completing the engineering, prototyping, testing and construction of the cross-hair system on time and on budget
- BLMs may provide partial backup for Budal monitor functions after beam commissioning