# Presentation: 878050

## NuMI Target: Today and Tomorrow

_**Outline:**_
-  NuMI Beam Parameters
-  Design Constraints
-  Thermal and Stress Analysis
-  Instrumentation
-  Radiation Damage
-  Target Tests
-  Upgrade to 1.6 MW(+)

## Beam Parameters and Upgrade Path

- NuMI beam design parameters:
- 0.4 MW beam power
- 120 GeV/c proton beam
- 4x1013 protons per 8.6 sec beam spill
- 1.87 sec repetition rate
- 1 mm RMS circular beam spot size
- Upgrade path considered to 1.6 MW (+) design:
- 120 GeV/c proton beam
- Double number of protons per spill
- Double repetition rate  (higher repetition rate easier to handle than instantaneous)

## NuMI target

- IHEP Protvino design team
- 	V.Garkusha, V.Zarucheisky
- 	F.Novoskoltsev, S.Filippov, A.Ryabov, P.Galkin, V.Gres, V.Gurov, V.Lapygin,
- 	A.Shalunov, A.Abramov, N.Galyaev, A.Kharlamov, E.Lomakin, V.Zapolsky
- FNAL design team
- 	J.Hylen, K.Anderson
- FNAL beam test
- 	J.Morgan, H.Le, Alex Kulik, P. Lucas, G. Koizumi
*	**	**Energy deposition calculations done with MARS*
*	**	**Target construction done at IHEP*

## How  beam is produced

## Different  spectra obtainedby moving target and 2nd horn

- MINOS on-axis:

- -> Target in horn
- (L.E. configuration)

##  spectra moving off-axis( unoscillated, GEANT M.C. )

- Off-axis detector experiment probably prefers M.E. configuration (target outside horn)

## NuMI target types

- Low Energy Target must fit in horn
-       Medium Energy Target
-          has more space for cooling,
-            target outer vessel gets less beam

## Low Energy Targetwill be used for MINOS

- Graphite Fin Core
-                     2 int. len.
- Water cooling tube
-   also provides mechanical
-      support
- Aluminum vacuum tube

## NuMI Prototype Target M.E. style section used in beam test

- Ignore instrumentation
-   on ends

- Target fins

- Beam
- direction

- Water cooled
-    pressing plate

- Space between fins prevents buildup of dynamic stress along beam direction

## Neutrino targets should be long, narrow, low density(less true for L.E. :  larger angle + less horn depth of field)

- proton

- +

- (P ~ 3 – 30 GeV/c for useful pions)

- Target

- Narrow target lets  escape out sides
- 		*but*
- 	Small p-beam spot size -> high stress

-  peak= 0.1 to 0.01  (Pt ~ 0.3 GeV/c peak production)

- Lescape

- Rtarget

- Example:
-     For Rtarget = 3 mm         =>       Lescape = 3 cm to 30 cm
-                                                                              compared to 48 cm int. len. for graphite
*NuMI full width of fin:   6.4 mm (L.E.)   /   3.2 mm (M.E.)*

## Target – Low Energy Version(Low Energy refers to neutrino spectrum, not beam power)

- Narrow – location checked by scanning beam across edge.
- Sense by:
-   (i) charge (delta-rays) knocked out (wire connected to target) (called Budal)
-   (ii) scattered beam  into cross hairs ionization chamber (BLM)

- Casing of target fin electrically insulated from base.
- Wire strung from case to top of module.  When moving,
-  can sense if case touches horn by short to “ground”.

## Target Temperature- lots of headroom

-  Instantaneous temperature
-     - room for large factor increase,
-       far from even sublimation (~2000 C)
-  Heat easily conducts to water line,
-     many times average load no problem
* **Would want to increase diameter of*
*  **water line to allow for more flow*
*    **so L.E. target does not warp*

## Target dynamic stress?(Approximately linear with instantaneous protons)

- Current safety factor of 3.8
-    at fin center
-    – can increase with:
-          larger spot size
-          different graphite (next slide)
- Current safety factor of 2.2
-      at curved edge of fin
-      – can increase with:
-          different graphite (next slide)
-          thicker fin (at some cost in )
- Our target concept evolves
-    reasonably well to double the
-       instantaneous proton rate

## Target Material - Graphite

***(Higher A would give more pi for low energy beam,***
***but energy density becomes problematic)***

**Graphite R7650 has figure-of-merit K = 0.66,****                   ****	****presumably improves safety ****factor by x 1.4 over NuMI ZXF-5Q**
**Carbon-fiber/carbon-matrix composite materials may be even better**

- From L.Bruno, CERN

## Budal for L.E. target

- In current design, downstream end of aluminum vacuum tube reaches 190 deg C
-   - it is insulated from water cooling to allow Budal monitor to work.

- For higher beam power,
-   must connect this tube
-  to water cooling –
-   probably giving up Budal
-           *(alternative – make *
*          **casing from Be?)*
- Budal could be retained
-  in M.E. target

## Radiation Damage

*Most radiation damage info is*
* **from reactor neutrons*
- In this example, graphite self-
-  destructs at  ~ 2x1020 n/mm2
- Highest radiation density in
-  NuMI target is proton spot
-  near entrance
-     ~ 0.5x1020 p/mm2 / year
- NuMI target test accumulated
-  0.023x1020 p/mm2
-  with no visible damage
- Target longevity uncertain
-  – will gain experience in 2005

- Radiation Damage and Life-time Evaluation of RBMK Graphite Stack, *XA9642904*,
- P.A.Platonov, O.K.Chugunov, V.N.Manevsky, V.I.Karpukhin, Russian Research Center Kurchatov Institute

## Any fall-backs in case of rapid radiation damage ?Factor of a few:

- Drive motors

- Shielding
- Module

- Target Carrier

- Increase spot size
-   along fin
-   (current L.E. could
-    increase both directions)
- 2)   In case of M.E. style,
-   periodically move fin
-   to get fresh material
- Modest loss in efficiency
-   further from top of fin
-  *Target module already*
*  **has capability to do this*

## Target Test Conditions

- Goals:
-  High stress pulses cause visible damage?
-  Radiation cause visible damage?
-  Budal monitor work for beam alignment?
-  Graphite vs Beryllium

- PROPOSAL

- Prototype thinner fin, smaller spot
-   to obtain similar stress, temperature
- Highest stress pulses in test 1013 protons
-   0.21 mm x 0.16 mm calculated to be
-                                at non-fatigue stress
-                                limit
-                                -- no visible damage
- 		under microscope !
- 		    *target test used:*
- 		7x1017 protons
-   		3x105 pulses
- 		mostly 0.2x1013ppp
- 		0.2 to 0.3 mm RMS

## Target Budal Monitorin test beam

- Electrically insulate target
- Scan beam across target
- Delta rays knocked out induce target voltage
- Electronic readout of target = Budal Monitor
- Highest signal is at edges of target
- Better signal-to-noise for target-in-vacuum
-                                          than target-in-He
- In Helium, insulator coated (silicon nitride) graphite
-    gets less background than bare graphite
- Can locate target to ~ 0.1 mm

-  1.8 mm
-    target

- VBudal

## Target Upgradesummary

-     New target,  but water-cooled graphite
-      probably OK
-              *if*
-   radiation damage
-      lifetime OK

## Conclusion

- NuMI–style target with modifications look good for 1.6 MW (or even higher) beam
-                       *with caveat that radiation damage lifetime not known*
- Modifications:
-       Probably choose different grade of graphite
-       Increase water cooling tube diameter
-       M.E. style target is more robust – good for off-axis
-       Cool (or change material) of outer can for L.E. style target