The MiniBooNE Horn

NBI 14-19 March 2002

The MiniBooNE Horn

Ioanis Kourbanis

For

The MiniBooNE Collaboration


Outline

List of people Horn characteristics Horn Power Supply Horn Striplines Highlights of Horn Construction and Assembly Horn Testing Horn Changeover Future Plans


List of People• C. Anderson

• L. Bartotzek (Bartoszek Engineering)

• L. Bartelson

• L. Bugel

• C. Jensen

• H. Le

• B. Markel (Markel & Associates)

• J. Misek

• F. Nezrick

• H. Pfeffer

• R. Reilly

• D. Snee

• M. Sorel

• E. Zimmerman


Horn Characteristics

We are using one horn with a narrow neck and a conical inner conductor (BNL Design) designed to run at a current of 170 KA.

The horn is made out of Al alloy 6061-T6 and is excited by a 143 sec current pulse. Keep the voltage at the PS below 10 KV (use solid state SCR’s

instead of thyristors) Reduce the current pulse width as much as possible to avoid

excessive heating of the horn . Keep the voltage at the horn as low as possible (small inductance).

The horn will operate at an average rep rate of 5 Hz. Total average power deposited in the horn is 2.4 KW.


3-D Model of the Horn


Horn Power Supply

The Power Supply consists of a Capacitor bank (1,344 F) discharged through an inductive load by an SCR switch. The system has a separate circuit for energy recovery.

The circuit is divided into 16 parallel capacitors, each with its own SCR switch.


Horn PS Parameters

DESIGN OPERATION

Pulse Amplitude(KA)

250 170

Rep. Rate(Hz)

7.5 5.0

Circuit Inductance(microH)

1.78 1.33

Operating Voltage(kV)

9.5 5.4

Average Power(kW)

62 19


Power Supply Schematic


Power Supply View (Front)


Power Supply View (Back)


Horn Stripline Balanced design (odd number of conductors) to

minimize forces. The conductor spacing is 1 inch. Fluted alumina

insulators with a 2 inch creepage length were used to separate the conductors.

The test stripline piece, along with a clamped joint, were corona tested.

The inductance of the final stripline was measured to be 18.5 nH/m.


View of the Long Stripline Section


View of a Stripline Joint


View of the Small Stripline Section


Construction and Assembly Highlights

Forged Outer Conductor The water sprayers were vibration isolated from

the Horn Outer Conductor. Solid connections from the striplines to the Horn. The Horn Inner Conductor was welded at

Fermilab using a programmable TIG welding machine.


Outer Conductor after Forging


Outer Conductor after Machining


Outer Conductor after Welding


Water Manifolds


Water Truss


Water Truss and Water Manifolds


Water Truss Bellows Detail


Water Connection Detail


Outer Conductor with Water Truss


Water Drain Connection


Water Nozzle Detail


Twist Transitions


Inner Conductor Before Welding


Hand Scraping before Welding


Welding Sample


Large Weld


Small Diameter Weld


Inspecting the Small Diameter Weld


Radiography of Weld


Radiography of Large Weld


Moving the Inner Conductor from The Welding Machine


Inserting the Inner into the Outer Conductor


Horn Testing

The horn was pulsed for the first time on 07/27/01. The horn test was completed on 02/12/02 after completing 11M pulses

at full current. We completed horn magnetic field measurements. Completed a series of vibration measurements. Things we were monitoring:

Total current Current in the four striplines feeding the horn Total voltage Cooling water supply and return temperatures Horn temperatures


Overview of MI-8 Test Area


Horn module overview


Stripline Configuration at the TSB


Current and Voltage Profiles


Horn Magnetic Field Measurement


Horn Temperature Profiles with Different Sprayer Configurations


Correlation between Horn and Water Return Temperatures


Horn Vibration Spectrum


Horn Axial Displacement vs. Time


Horn Changeover

The horn module is expected to be highly radioactive (30 Rad/hr at 2 ft).

In order to reduce the Radiation Exposure to under 100 mR/hr at 1 ft, the shielding requirement is 5” of steel on all sides.

Because of the crane lifting capacity, two separate coffins (an inner and an outer ) will be used.

The inner coffin has 1.5’’ thick walls except from the top cover and the front door (5” thick).

The outer coffin has 3.5” thick walls and is open at the top and the front.


Horn Changeover (2)

The radioactive horn module will be stored inside the two coffins in the Target Service Building in the old Proton Line.

Four coffins (two inner and two outer coffins) will be needed for a changeover.

A detailed procedure outlining all the steps for a changeover has been written and reviewed.

Total estimated time for a changeover is 2 weeks.


Inner Coffin


Outer Coffin


Initial Configuration


Inner and Outer Coffins


Open Inner Coffin Door


Position the Coffins next to the Horn Module


Pull the Horn Module in the Coffin


Close Inner Coffin Door


Future Plans

We have started disassembling the Power Supply and the Striplines.

The horn modules will be stored in the inner coffin. Plan to install the horn in the target pile on May 7. We estimate to be ready for a horn changeover test on May

15. We should be ready for beam on June 15. We have started ordering the large pieces for a spare horn.

Documents

The MiniBooNE Horn