[old_tv_nut]

25kv is starting to produce X-rays, and unlike color CRTs, that one most likely does not contain enough lead or thickness to reduce them. As said above, standing back several feet should be good enough protection. Also, X-ray effects are cumulative, so if you just have a quick look to see the shape of the circle, no problem. As an additional measure, you can turn down the brightness and run at much lower beam current for direct viewing.