# Presentation: 608279

## Study of Pion Capture Solenoids for PRISM

- _H.Ohnishi_ AB
- M. Aoki C, Y. Ajima A, N. Fukasawa AD, K. Ishibashi B, Y. Kuno C,
- T. Miura A, K. Nakahara C, T. Nakamoto A, N. Nosaka C, M. Numajiri A,
- A. Sato C, N. Shigyo B, A. Yamamoto A, T. Yokoi A and K. Yoshimura A
- KEK A, Kyushu University B, Osaka University C,
- Tokyo University of Science D
- Nufact’03  June 7, 2003

**Notes:**
I study about pion capture solenoid for PRISM, especially on radiation heating from the target. 

## Outline 

- Introduction
- Pion capture solenoid for PRISM
**A Model Experiment to Measure Radiation Heat Load**
- Experimental set up
- Measurement
- Results
- Comparison with simulation results (MARS)
- Further R&D plan
- Summary

**Notes:**
Outline is here.
I’m going to talk about the experiment mainly.

## Pion Capture Solenoid for PRISM

- PRISM needs the SC solenoid  required a high field (Bc = 6~12 T)
- Keep the solenoid at low temperature
- The solenoid is heated by radiations  from the target
- To reduce the radiation heat load, thick radiation shield is needed
- We estimate the radiation heat load with simulation code MARS,            but the accuracy of simulation results have not been studied

- 50GeV protons 750kW

- SC Solenoid

- Shield

- We experimentally evaluate         the accuracy of simulation results.

- PRISM

- Pion capture solenoid

**Notes:**
Everyone knows PRISM, so I skip the explanation of it.
In PRISM, we need the superconducting solenoid to be required a high field.
So we have to keep the solenoid at low temperature.
But, the solenoid is heated by radiations from the target, such as neutrons, protons,gamma ray, and so on. 
To reduce the radiation heat load, thick radiation shield is needed.
When we design the solenoid and the shield, we have to estimate the radiation heat load. 
Now, we estimate them with simulation code MARS.
But the accuracy of thermal calculations are hardly reported.
For the reason, we experimentally evaluate the accuracy off thermal caculations.

## A Model Experiment to Measure Radiation Heat Load

- Radiation heating in a model solenoid (mockup) was precisely measured
- The experimental results were compared with                          the result obtained by MARS

**Notes:**
We have performed a model experiment to measure radiation heat load.
In the experiment, Radiation heating in the model solenoid was precisely measured. 
We call the model solenoid mockup.
Then, the results were compared with the simulation code MARS.
There is conducting cooled R&D solenoid in KEK. And this mockup modeled it.

## Experimental Conditions(KEK 12GeV-PS)

**Experimental Conditions**_**(KEK 12GeV-PS)**_

- Beam parameters
- 12 GeV proton
- Intensity ~1011 (protons/sec)
- Slow extraction
- Experimental area
- At upstream of EP2-A dump

- KEK
- 12GeV-PS
- main ring

- Beam Dump

- Experimental area

- 1 m

- EP2

- A-line

**Notes:**
We have performed the experiment at KEK 12GeV proton synchrotron,and set the installation like this.
Beam parameters were as follows.

## Experimental setup

_**Experimental setup**_

- 12GeV primary protons 1011(p/s)

- Sensitive measurement of radiation heat load to the mockup      with the cryo-calorimeter

**Notes:**
This is experimental setup.
Primary protons go through the beam monitors and hit the target, like this.
Then, many radiations are produced and heat this mockup.
We made sensitive measurement of the radiation heat load to the mockup with this cryocalorimeter.
I’ll talk its details later.

## Experimental Installation

- Beam dump

- 12GeVPS

- primary protons
- 12GeV ~1011(p/s)

- Mockup

- 240 mm

- Cryostat

**Notes:**
This is experimental installation.
This is cryostat, and mockup is in it, like this.
Primary protons come from PS, through the bore in the cryostat, and finally reach to the dump

## Profile & Intensity of Primary Protons

| Cu foil area (mm) | intensity
(protons/sec) | fraction (%) |
| --- | --- | --- |
|  20 | 6.70 (0.45)  1010 | 99.92 |
|  20_30 | 3.14 (0.26)  107 | 0.05 |
|  30_40 | 1.19 (0.09)  107 | 0.02 |
|  40_50 | 8.00 (0.77) 106 | 0.01 |

- Target size 30 → >99.9 % protons bombard the target
- SEC count rate       23.16 (counts/sec)	             Calibration result   2.89  0.19 (109 protons/count)

- Mockup

- Target (off)

- SEC

- Cu foil

- primary protons

- Activate!

- Profile of Primary Protons

**Notes:**
We checked the profile of primary protons to activate copper foil.
The table shows most primary protons,over 99 percent, go through within 20 mm in a diameter.
And, the target size is 30 mm in a diameter, so we confirm most protons bombard the target.

## Highly sensitive measurement   by cooling the mockup (20 K)
Highly sensitive thermometers (resolution < 20 mK)
Quick response because of small specific heat

- Highly sensitive thermometers (resolution < 20 mK)
- Quick response because of small specific heat

- Mockup temperature rise up* ** ****T** **= **Q** ** **K*at thermal equilibrium state
- Q : Heat load
- K : Thermal conductance determined by thermal shunt
- Thermal shunt determines the relation between mockup temperature and heat load

- _Cryo-calorimeter_

**Notes:**
I explain about cryocalorimeter.
We realized highly sensitive measurement for cooling the mockup at low temperature.
The reason of that, we can use highly sensitive thermometers,
and we can get quick response because of small specific heat.
Cryo-cooler cooled this mockup through the thermal shunt,
The thermal shunt determined the ratio of mockup temperature to heat load.

## How to Measure Radiation Heat Load

- Mockup

- Mockup

- Mockup

_**How to Measure Radiation Heat Load**_

**Notes:**
Now, I show you how to measure.
This is cryo-calorimeter.
At first, radiations heat the mockup. The heat load is Qbeam. And I want to know this value.
After of that, they were in thermal equilibrium state in this time.
We define the equilibrated mockup temperature as T beam. 
Then, we stop the radiation heating by target off.
Next, we heat the mockup by the heater. And this heat load is Qheater.
After of that, they were in thermal equilibrium state again.
we define the equilibrated mockup temperature as Theater.
Now, when Theater is equal to Tbeam, Qheater is equal to Tbeam.
I got it.

## Typical Experimental Data

_**Typical Experimental Data**_

- Tbeam  =  Theater →  Qbeam  = Qheater

- Qheater

- Qbeam

- Thermal balance Theater

- Thermal balance Tbeam

- Target on / off

- Target off
- Heater on

- Target on

- Heater off Target on

- heater

**Notes:**
This is real data.
Actually, one measurement spent about 12 hour.
Time constant is about 30 minnutes in this time

## Experimental Results

| Target position (mm) | Radiation heat load (W at 1011 protons/sec) |
| --- | --- |
| -80 | 0.34  0.02 |
| 0 | 0.88  0.06 |
| 80 | 1.42  0.10 |

- 12GeV
- primary protons

- 0

- 80

- -80

- Target position

- Overall error is nearly equal to 7 %

**Notes:**
This table shows experimental results.
Target position is here. And primary protons come from left side.
We normalize radiation heat load at the beam intensity.
The reason of that, forward radiations are more than backward ones.

## Comparison with simulation results 

- 12GeV
- primary protons

- 0

- 80

- -80

- Target position

- Overall error < 7%

**Notes:**
This figure shows radiation heat load as a function of target position.
There are data points. Experimental results.

##  Experimantal Summary

- We have performed direct measurement of radiation heat load.
- Experimental results are 20-30% higher than simulation results
- Experimental results show the consistent dependency with simulation.

**Notes:**
read them

## Further R&D Plan forPRISM Capture Solenoid

**Notes:**
Next, I’ll talk about further R&D plan for PRISM Capture Solenoid.

## Base-line Parameters for PRISM Capture Solenoid

- Boundary condition
- The maximum transverse momentum
- 		 Pt = 300  B  R/2	= 90 MeV/c
- Central field		Bc = 6 T
- Effective bore		R = 0.1 m

**Notes:**
PRISM capture solenoid requires this boundary condition
The maximum transverse momentum is equal to  90MeV/c
Now, we assumed solenoid central field is 6T,
Effective bore determines 0.1 m in a radius.

## Solenoid Parameters

_**Solenoid Parameters**_

- Parameters
- Central field			6 T
- Coil length ( 2 target length)	1.6 m
- Stored energy / solenoid mass ratio	10 kJ/kg
- Solenoid inner radius 		x
- Al stabilized NbTi cable
- Radial thickness
- Beam pipe	 0.1 m
- Radiation shield	 f(x)
- Vacuum insulation 	 0.05 m

**Notes:**
To determine the solenoid geometry
We assume possible parameters as follows.
Then , taking the Solenoid inner radius as variable parameter.
To optimize solenoid inner radius, I calculated radiation heat load and solenoid stored energy

## Radiation Heat Load & Stored energy  vs. Solenoid radius

**Radiation Heat Load & Stored energy**_**  vs. Solenoid radius**_

- 50GeV protons (750kW)

-    Materials
- Target C(graphite)
- Shield W
- Solenoid Al stabilized NbTi

**Notes:**
This figure shows radiation heat load and stored energy as a function of the solenoid inner radius
Red line is the heat load and black line is stored energy.
Heat load gets higher with smaller inner radius while stored energy does opposite.
So we have to make compromise.
Here I took 0.45 m as an optimized value.
In this assumption If we can cool 500W heat load, we can design PRISM capture solenoid.

## Preliminary design Parameters

_**Preliminary design Parameters**_

|  | PRISM |  |
| --- | --- | --- |
| Central field(T) | 6 |  |
| Shield thickness(m) | 0.25 |  |
| Solenoid radius(m) | 0.45~0.55 |  |
| Length(m) | 1.6 |  |
| stored energy(MJ) | 16 |  |
| Heat load(W) | 470 |  |

**Notes:**
Taking those assumption, and the optimized value, the preliminary design parameter can be as follows

## Small Size R&D Solenoid

_**Small Size R&D Solenoid**_

|  | PRISM | R&D(1/2.5scale) |
| --- | --- | --- |
| Central field(T) | 6 | 3~6 |
| Shield thickness(m) | 0.25 | - |
| Solenoid radius(m) | 0.45~0.55 | 0.2~0.24 |
| Length(m) | 1.6 | 0.4~0.6 |
| stored energy(MJ) | 16 | 0.5~1 |
| Heat load(W) | 470 | 470/(2.5)3 = 30 |

- R&D solenoid

**Notes:**
In order to search the engineering feasibility. We are planning to make a small size R&D solenoid.

## Summary

- We have performed direct measurement of radiation heat load
- Experimental results are 20-30% higher than simulation results
- Experimental results show the consistent dependency of target position with simulation
- We are planning R&D with a small size solenoid

**Notes:**
read them

## Error Breakdown

- (%)

- * T.Asano et al, 'Target dependence of charge distributions in spallation reactions of medium-mass nuclei with 12GeV protons' , Phys. Rev. C 28, 1718(1983)

| Target position (mm) | -80 | 0 | 80 |
| --- | --- | --- | --- |
| *12GeV proton – Cu 
24Na production cross section | 5.1 | 5.1 | 5.1 |
| Ge detector efficiency | 4.3 | 4.3 | 4.3 |
| Fluctuation of beam intensity | 2.1 | 0.8 | 1.3 |
| Measurement of heat load | <1 | <1 | <1 |
| Total error | 7.0 | 6.8 | 6.8 |

**Notes:**
Error breakdown is here.
12GeV proton –Cu Na24 production cross section and Ge detector efficiency almost determine total error.
These two parameters are needed to evaluate beam intensity.

## Mockup & Target

- Target

- Mockup

- Mockup
- Made of copper
- Set resistive heater
- Thermometer
- High sensitivity at low temperature
- Four terminal measurement
- Target
- 0.2 interaction length
- Movable
- Made of copper

- 130

- 170

- 180

- 280

- 240

- 30

- 30

- C20

- Resistive heater

- Thermometer

## Heat load measurement has need to thermal equilibrium state
Target position move to up-stream
	higher radiation heat load
	Many secondary particles fly out forward

- Target position move to up-stream
- 	higher radiation heat load
- 	Many secondary particles fly out forward

- _Typical Experimental Data_

- A

- B

- C

- 12GeV protons (<200W)

**Notes:**
各位置でどの位の入熱かを書く。

## Difference between Tbeam and Theater

- Difference between Tbeam and Theater  <  0.15K

- Tbeam & Theater

## Plot Qheater vs.Theater

**Plot Q****heater**** vs.T****heater**

***T** **= **Q** ** ***

## Correcting Qbeam with difference between Tbeam and Theater

**Correcting Q****beam**** with difference between T****beam**** and T****heater**

- Effect of the difference between Tbeam and Theater < 1%

- Qheater

- Qbeam

## Fluctuation of Beam Intensity

- Fluctuation of beam intensity (protons/10min)  <  3%

- Mockup temperature

- Beam Intensity

**Notes:**
モックアップ温度の時定数は2000~4000(sec)なので、10minに比べて充分大きいと言える。

## Tbeam & Theater at Various Thermometer

**T****beam**** & T****heater**** at Various Thermometer**

- T =  Tbeam - Theater

- cryocooler

- Mockup

- TCold

- TShI-L

- TShI-H

- TMoI-L  TMoI-H

- Tbeam

- Theater

## Effect of Outside Mockup

- Theater

- Tbeam

- Temperature of outside mockup is nearly constant.
- Effect of outside mockup to Tbeam & Theater hardly changed.

- Tbeam

- Theater