wikipedia..not great i know but an idea

Solitary confinement is a punishment or special form of imprisonment in which a prisoner is denied contact with any other persons, excluding members of prison staff. It is considered by some as a form of psychological torture.[1] It is usually cited as an additional measure of protection (of society) from the criminal. It is also used as a form of protective custody.
Solitary confinement is colloquially referred to in American English as the 'hole', 'lockdown', the 'SHU' (pronounced 'shoe') or the 'pound', and in British English as the 'block'.

Those who accept the practice consider it necessary for prisoners who are considered dangerous to other people ("the most predatory" prisoners),[2] those who might be capable of leading crime groups even from within, or those who are kept 'incommunicado' for purported reasons of national security. Finally, it may be used for prisoners who are at high risk of being attacked by other inmates, such as paedophiles, witnesses, or celebrities who are in prison themselves. This latter form of solitary confinement is sometimes referred to as protective custody.
In the US Federal Prison system, solitary confinement is known as the Special Housing Unit (SHU),[3] pronounced /ˈʃuː/. California's prison system also uses the abbreviation SHU, but it stands for Security Housing Units.[4] In other states, it is known as the Special Management Unit (SMU), pronounced /ˈsmuː/.
Opponents of solitary confinement claim that it is a form of cruel and unusual punishment[5] and torture[6] because the lack of human contact, and the sensory deprivation that often go with solitary confinement, can have a severe negative impact on a prisoner's mental state[2] that may lead to certain mental illnesses such as depression or an existential crisis[7][8][9][10][11] and death[6].