Avignon has a wide range of hotels but they book quickly in the summer season...
Participants are expected to make their own arrangements as no block reservations can be provided. If you do not wish to book via the usual web-based sites, Avignon Tourism has provided more information via their excellent Avignon Tourism website.
Be careful of unsolicited "Dear Professor" phishing e-mails asking for your travel dates to Avignon and proposing accommodation from the "Traveller Team" at travellerpoint.org...