I have been recently performing experiments using UVB (and UVA light) light.
The personal protection I have been using have been a welder's mask (to protect the face) and sun glass like material for the eyes and sun protective clothing that did not leave any skin exposed (e.g. hands, arms etc).
As mentioned in the comments, surround the experiment in a glass shield, or standing behind a glass shield could be an option. According to the article Photoprotection by window glass, automobile glass and sunglasses (Tuchinda et al. 2005), states that the main factors for broad UV (UVB and UVA) protection are:
The degree to which glass products provide UV protection depends on the glass type, glass
color, the presence of an interleave between pieces of glass, or the presence of a coating on the glass.
They also state that the dark tinted glass sometimes used on office buildings provides broad UV protection.
As UVA is also potentially dangerous (depending on dose), Tuchinda et al. (2005) also conclude that
Recent developments in the glass industry have resulted in the introduction of additional filters for
UVA and infrared radiation. This UVA filtering technology can now be incorporated into a glass
coating, providing more comprehensive photoprotection.