Encountering former, abusive advisor at a conference I'm a PhD Student in the US and am going to a conference for poster presentation soon.
I just realized that my poster will be right next to my former advisor's poster (To be precise, it's his student's poster).

To explain the history with the advisor, I worked with him for about a year. But he was emotionally abusive and unsupportive. I had panic attacks whenever I had a meeting with him. After a year in the program, I quit and applied to another program again. This second program has worked out really well, and I'm very happy with my current advisor.

The separation with the former advisor seemed okay at first (he wasn't upset or angry about my decision at least when I talked about it. He sounded like he understands my decision). But then, after the conversation, he started ignoring me, which means that he wasn't okay at all.

The thing is that I'm now having a panic attack and become very anxious after realizing that my poster is right next to his. It seems unavoidable to run into him at the conference.

I'm really stressed out as this reminds me of all the traumatic events I had gone through. But at the same time, I want to use this opportunity to overcome this anxiety associated with him.

Can anyone give me advice on how I should react when I see him at the conference? How can I react in a professional way? Should I just ignore him? I can say hi to him, but I'm concerned that he will ignore me (This happened previously, and likely to happen again).

Any suggestions or advice will be appreciated!

UPDATE: Thank you all for very helpful suggestions and support! I think it's too late to relocate my poster. But after reading all the comments, I start to think maybe I just misinterpreted his neutral response or indifference as something negative or aggressive. Maybe I was overreacting initially. After reading everyone's comments, thinking about it for a couple of days really helped me reappraise the situation. Thanks all!
This doesn’t answer your explicit question, but have you considered sending an email to the conference organizers asking for your poster to be reassigned to a different part of the poster presentation area so that it’s not right next to the former adviser’s poster? This could go a long way towards minimizing the possibility of trouble, and will probably make it easier for you to handle the task you have set yourself of overcoming the anxiety you have related to meeting him at the conference, while leaving you some wiggle room to maneuver in case that turns out to be more difficult than you expected.

The email doesn’t have to go into details, just say this is a person you’ve had some conflict with in the past and you would prefer for your poster not to be close to theirs. If I were an organizer I’d be more than happy to accommodate such a request. 

Good luck, I hope things go smoothly and that you’re able to focus on sharing your work with others and having fun.