Eliminating Nuclear Bombs with Ultra-High Energy Neutrinos

Hiroyuki Hagura (KEK)

Hirotaka Sugawara (Univ. of Hawaii)

Toshiya Sanami (KEK)

Outline

• Introduction
• Mean free paths of neutrinos
• What is a nuclear weapon?
• How to eliminate the nuclear weapons from the other side of the Earth?
• Muon accelerator design
• Conclusions
• Discussion

Introduction

• Non-proliferation of nuclear weapons is difficult at present in spite of the existence of NPT.
• Detecting nuclear bombs globally and eliminating them safely are very important for global security.
• Interestingly enough, neutrino is considered to be the only particle that is capable of doing that on the global scale.
• Big collaboration of particle, nuclear, reactor and accelerator physicists and security experts will play an essential role for the purpose.

Cross-sections for neutrino-nucleus scattering process

Consider a neutrino of energy E scattering off a target

nucleus X of proton number Z and neutron number N :

ν

Mean free paths of neutrinos

• Calculated at the tree level
• Only two flavors (u and d quarks) are included
• Scaling functions with no QCD corrections
• No neutrino oscillation is assumed
• Protons and neutrons are uniformly distributed inside the Earth
• If one includes several effects, the cross-sections will become a few times larger, leading to smaller mean free paths

What is a nuclear weapon?

1. Ignition by explosives
2. Shock wave is created, density wave makes Pu and U go beyond the critical point
3. Initiator gets broken (aluminum foil)
4. In 10 sec super-critical fission reaction occurs everywhere in the core
5. Tamper works to suppress “fizzle explosion”
6. Full explosion produces a bomb yield of ~20 kt

-6

explosive A

explosive B

ignition

system

initiator

Pu core

U tamper

238

239

239

238

How to eliminate them from the other side of the Earth?

1. Hadron shower hits the target bomb and causes sub-critical nuclear fissions
2. The temperature of the bomb increases
3. Above 250 degrees the surrounding explosives (dynamite) get ignited
4. The rest of the process is the same as the `ordinary’ nuclear bomb explosion

hadron shower

nuclear

bomb

neutrino beam

Muon

accelerator

inside of the Earth

E ~ 100 – 1000 TeV

Mean free path = diameter of the Earth

ν

The important difference!

1. The bomb is exposed to hadron beams which play the role of initiator.
2. The beams cause sub-critical chain reactions to start before the shock wave reaches the center
3. Such a phenomenon is well known as the ``fizzle explosion”
4. This makes the destruction of the nuclear bomb relatively safe.

shock wave

shock wave

initiator

Pu core

hadron shower

What are the required parameters?

• 10 fissions per 10 kg of Pu to reach 300 degrees.
• 10 fissions per 10 kg of Pu to vaporize all the plutonium. This is needed when the plutonium is stored away from the explosive material.

16

239

239

19

We can calculate numerically how many neutrinos

are needed to reach this value in a given time.

Numerical results – tentative

• For E = 1000 TeV neutrinos, the required number of neutrinos is 10 in a few seconds.
• For lower-energy neutrinos, we will need more larger intensity.

14

ν

Using three MC programs, that is, HERWIG6,

MARS and MCNPX, we have obtained:

Muon accelerator design

• Two synchrotrons A and B, which are ~100km in radius and revolvable, encircle a large mountain.
• Muons emit neutrino beams along the straight sections P P and Q Q , aiming at target bomb(s) placed on the opposite side of the Earth.
• However, large synchrotron radiation takes place, which is very difficult to overcome.

synchrotron A

synchrotron B

hazardous

plane 2

hazardous

plane 1

neutrino radiation ``hot spot’’

injection system

+

μ

μ

-

2

1

2

1

Is it practical to do so?

1. Can we steer the beam?

Δθ ~ 10 (rad)

-- Not easy but possible

Current achievement Δθ ~ 10 (rad)

• Can we make 10 neutrinos in a short period, for example, in ~ 1 sec?

-- High-intensity proton machine (now ~ 10 /sec)

• Can we make a 1 PeV machine?

-- The hardest problem (now ~ 1-10 TeV)

Number of questions

-7

-6

13

14

Conclusions

• UHN neutrinos can be very useful:
• Global disarmament
• Earth tomography (X-ray by neutrino)
• Perhaps communication (a prototype of SETI)
• Technology development:
• Invention of much stronger magnet ~10Tesla
• High-energy, high-intensity accelerator
• Fine alignment
• Detectability of nuclear bombs (J. Learned)
• Financial support:
• Massive investment (~$50B) will be needed
• World-wide collaboration

Discussion

• More precise calculations of the cross-sections for neutrino-nucleus scattering:
• More information on the structure functions of Pu/U
• Further numerical studies (now in progress):
• Determination of the precise value of the beam energy and intensity required for destruction/detection
• Effect of UHE neutrinos on nuclear reactors in operation
• Another design of the 1 PeV muon accelerator:
• Linac more practical? (J. Learned, B. J. King)
• Other methods of producing UHE neutrinos:
• Constructing a huge accelerator on the Moon (J. Learned)
• Practical method of detecting nuclear bombs:
• Anti-neutrino detector will be used for the detection