BNCT

From the Proposal, April 2014:

1-1.  Boron Neutron Capture Therapy (BNCT)

BNCT utilizes the nuclear reaction:  
10B + [11B] a + 7Li + 2.31 MeV.
Alpha particle has very short range thus has the possibility of targeting a tumor without damaging surrounding healthy cells.  Boron 10B is planted in a tumor using chemicals such as:  
Polyhedral borane anion, sodium borocaptate or BSH (Na2B12H11SH).
Neutron is targeted to a tumor from outside.

1-1-1.  H+ ion Accelerator

Neutrons are produced using a small proton accelerator (<8 MeV).  The purpose of OIST BNCT is to create the first mass production model of this facility.  Based on the results from KEK and Tsukuba University collaboration (one of the “Four pioneering projects” applied to Tsukuba International Strategic Zone), it has become clear that a mass production model of a BNCT facility can be simplified with a reduction in the system size and cost.  For example, the beam energy could be produced with 5~6 MeV compared to the 8 MeV of Ibaraki; that energy could be produced with only an RFQ, and a single-beam klystron (SBK) used at Ibaraki could be replaced with a multi-beam klystron (MBK).  MBK is now well established through the R&D for the ILC (International Linear Collider).  By using a MBK, the necessary high-voltage for the klystron modulator can be lowered from -90 kV to -30~-50 kV.  Table 1 shows the OIST-BNCT linac conceptual design parameters.  The maximum accelerating energy of proton is 8 MeV and beam current is 10 mA, respectively.  The accelerator length including neutron conversion with collimator is about 15 m.  As for proton acceleration, RFQ (Radio Frequency Quadruples linac) and DTL (Drift Tube Linac) are utilized.  A compact MBK (Multi Beams Klystron) and modulator developed by Ibaraki-BNCT program are also used.

Table 1:  OIST-BNCT linac conceptual design parameters

Beam:  proton (50 kV H+ ion source + LEBT (low energy beam transport))
Energy:   8 MeV
Max. average current:  10 mA
Accelerating structure:
            RFQ (5 MeV) + MEBT (Medium Energy Beam Transport) + DTL(+3 MeV)
RF frequency:  400 MHz
Repetition rate:  <200 Hz (1~200 Hz + single shot mode)
Pulse width:  <1 ms (100 μs~1 ms) → max. duty factor: 20%
Compact MB Klystron:
            Three 0.5 MW MBK (multi-beam klystron, two for RFQ and one for DTL)
Compact Klystron modulator:  32 kV, 33 A
Irradiation room:  Two (medical + research)           
Building             
            dedicated: 400m2✕2 floor,
            Parallel establishment with heavy ion facility
            access to electricity, utility, office and medical treatment rooms → prepared at main facility
Routine Operation:  6 people (outsourcing)

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1-1-2.  High intensity with low radioactive neutron generator



Fig. 1:  Schematic diagram of the high-intensity neutron generator.

1-1-3  BNCT facility

Fig. 2:  Layout of the BNCT.

(without klystron, power supply, water cooling system and radiation shield)