**8. Offsite effective dose considerations for muon colliders**

TeV energy neutrinos do not behave according to conventional operational health physics experience at power reactors and contemporary accelerator facilities. As noted previously, neutrinos are electrically uncharged and only interact through the weak interaction. Their small, but non-zero, interaction cross section creates a unique situation in terms of the behavior of the neutrino effective dose, particularly in terms of the shape and energy dependence of their radiation profile. These properties will lead to a modification of conventional health physics dose reduction concepts when applied to planned muon colliders.

Basic radiation protection principles suggest that the effective dose at a given location is reduced if the exposure time is minimized, the distance from the source is increased, or shielding is added between the source and the point of interest (Bevelacqua, 2009, 2010a). These principles must be modified at a TeV energy muon collider. The time principle is still valid for muons and neutrinos. The neutrino and muon effective doses are reduced by decreasing the exposure time.

The distance principle is ineffective when neutrinos are involved. Since neutrinos interact very weakly, relatively long distances are not effective in significantly reducing the neutrino effective dose. In fact, the neutrino beam remains a hazard for hundreds of kilometers. However, distance will still be effective for reducing the muon effective dose.

Unlike other radiation types, shielding neutrinos increases the effective dose. The magnitude of the particle showers produced by neutrino interactions is governed by the quantity of shielding material between the neutrino beam and the point of interest. However, shielding muons is an effective dose reduction measure.

From the standpoint of TeV energy neutrino radiation, a linear muon collider has a number of advantages over circular muon colliders. Firstly, the radiation is confined to two narrow 108 Particle Physics

Although the effective dose results at the earth's surface are significant, they occur over a relatively small area. The results also assume a 100% occupancy factor for this small area, which is not likely. The magnitude of the neutrino effective dose merits significant attention and emphasis on radiation monitoring and control. For example, a 500 TeV muon beam would deliver an acute absorbed dose rate of about 1 Gy/s to a 3.2 cm diameter circle. This absorbed dose rate is sufficient to deliver a biological detriment to the body within seconds

Dose management controls will be similar to those enacted for direct beam exposures at conventional accelerators. Interlocks associated with beam misalignment are effective in limiting the probability that the beam is directed toward an unanticipated direction. However, additional methods to control the offsite neutrino dose must be developed because lethal exposures can occur in a very short time even though the areas involved are small. Subjecting the public to potentially lethal effective doses represents unique facility licensing challenges that must be addressed in facility safety analyses. Public perception and stakeholder involvement will be key elements in licensing TeV-PeV scale muon colliders. The need for public involvement in licensing and regulatory discussions becomes particularly important when high effective doses could result from facility operations.

TeV energy neutrinos do not behave according to conventional operational health physics experience at power reactors and contemporary accelerator facilities. As noted previously, neutrinos are electrically uncharged and only interact through the weak interaction. Their small, but non-zero, interaction cross section creates a unique situation in terms of the behavior of the neutrino effective dose, particularly in terms of the shape and energy dependence of their radiation profile. These properties will lead to a modification of conventional health physics dose reduction concepts when applied to planned muon

Basic radiation protection principles suggest that the effective dose at a given location is reduced if the exposure time is minimized, the distance from the source is increased, or shielding is added between the source and the point of interest (Bevelacqua, 2009, 2010a). These principles must be modified at a TeV energy muon collider. The time principle is still valid for muons and neutrinos. The neutrino and muon effective doses are reduced by

The distance principle is ineffective when neutrinos are involved. Since neutrinos interact very weakly, relatively long distances are not effective in significantly reducing the neutrino effective dose. In fact, the neutrino beam remains a hazard for hundreds of kilometers.

Unlike other radiation types, shielding neutrinos increases the effective dose. The magnitude of the particle showers produced by neutrino interactions is governed by the quantity of shielding material between the neutrino beam and the point of interest.

From the standpoint of TeV energy neutrino radiation, a linear muon collider has a number of advantages over circular muon colliders. Firstly, the radiation is confined to two narrow

However, distance will still be effective for reducing the muon effective dose.

However, shielding muons is an effective dose reduction measure.

**8. Offsite effective dose considerations for muon colliders** 

(Bevelacqua, 2010a).

colliders.

decreasing the exposure time.

beams that can be oriented to minimize the interaction of the neutrinos. A simple dose reduction technique orients the linear accelerators at an angle such that the neutrino beams exit the accelerator above the ground. This configuration minimizes the residual neutrino interactions with the earth and man-made structures. Secondly, the spent muons can be removed from the beam following collisions or interactions before they decay into highenergy neutrinos.
